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DIFFERENT METHODS OF PURIFYING 

WATER. 


By 

P. A. MAIGNEN. 

MEMBER, THE ENGINEERS 7 CLUB, PHILADELPHIA; ASSOCIATE, AMERICAN SOCIETY OF CIVIL ENGI 
NEERS, NEW YORK; MEMBER, NEW ENGLAND WATER WORKS ASSOCIATION, BOSTON; 
MEMBER, AMERICAN WATER WORKS ASSOCIATION - , MEMBER, AMERICAN PUBLIC 
HEALTH ASSOCIATION? MEMBER, AMERICAN ASSOCIATION FOR THE 
ADVANCEMENT OF SCIENCE; MEMBRE CORRESPONDANT, AS¬ 
SOCIATION G&NERALE DES INGENIEURS, ARCHITECTES 
ET HYGIENISTES MUNICIPAUX, PARIS. 


52 North Thirteenth Street, Philadelphia, Pa. 


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Read before The Engineers' Club of Philadelphia, November 17, 1906< 

















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[Authorized reprint from Vol. XXIV, No. i (January, 1907), of the Copyrighted PROCEEDINGS 
of The Engineers’ Club of Philadelphia.] 


DIFFERENT METHODS OF PURIFYING WATER. 

P. A. MAIGNEN. 

Read November 11, 1906. 

In the paper presented April 16, 1904, after a visit of the members 
of the Club to the Lower Roxborough Filter Station, certain advan¬ 
tages were claimed for preliminary filtration as a help to slow sand 
filtration. In the subsequent operation of the filters those advantages 
have been demonstrated, as shown by the report of the Bureau of Fil¬ 
tration of Philadelphia for the year 1904 (page 100). 

The results of Lower Roxborough are compared with those of Upper 
Roxborough. Both stations receive the same water, but preliminary 
filtration is employed at Lower Roxborough and not at Upper Rox¬ 
borough. 


Comparison of Water from the River and the Water Coming out of 

the Sand Filters. 


Loicer Roxborough 
(with preliminary filtration). 


Maximum reduction, turbidity.100.00 

Maximum reduction, bacteria. 99.85 

Minimum reduction, turbidity. 81.81 

Minimum reduction, bacteria. 98.33 

Average reduction, turbidity. 96.02 

Average reduction, bacteria. 99.66 


Upper Roxborough 
(nopreliminaryfiltration). 

95.65 

99.81 
83.33 
95.70 
89.78 

98.81 


1 








2 


Cost of cleaning filters (page 176): 

Number of runs. 26 

Average cu. yds. of sand scraped per run .120 
Average million gallons filtered per run.. 123.7 
Average million gallons filtered per acre. . 233.4 


Cost per million gallons of water to scrape, 

transport, wash, and restore sand. . . $1.13 

Other expenses charged. 3.43 

Total cost of maintenance and opera¬ 
tion. $4.56 

Average net output of filtered water: 

Total filtering area. 2.65 

Average daily output.8,430,000 

Average yield per acre per day.3,190,000 

Sedimentation capacity. \\ days 


43 

117.75 

78.3 

108.9 

$1.85 

3.47 

$5.32 


5.60 acres. 
9,530,000 gals. 
1,700,000 gals. 


15 days 


Typhoid Fever Cases, Rate Per 100,000 Population. 

Wards 21 and 22 ( Which Receive 

Filtered Water from Lower City of Philadelphia {Excluding 

and Upper Roxborough) Wards 21 and 22). 

3.51 per 100,000 8.75 per 100,000 

Reduction, 59.7 per cent.,—presumably due to the improved quality of the 
water. 


The filtering area of the Lower Roxborough sand filters is a little 
less than half that of the Upper Roxborough filters, and the net rate 
of filtration at the former station is nearly twice as high as that of the 
latter. 

The maximum rate of filtration at Lower Roxborough was 5 million 
gallons and at Upper Roxborough 3 million gallons per acre per day. 
The difference between these rates and the net results given above 
arises from the fact that when the slow sand filters are started the rate is 
at first very low—0.5 million gallons; then it is increased to 1 million 
gallons and later to 2 million gallons and above. The time during which 
the filters are out of service for scraping, cleaning, and resanding also 
helps to account for the difference between the maximum and the net 
effective rates. 

The quality of the filtered water at the Lower Roxborough Station 
has been somewhat better than that of the Upper Station, notwith¬ 
standing the fact that at the latter the sedimentation is ten times 
greater than at the former. This result it evidently due to the use of 
preliminary filtration. 

Preliminary filtration, first established on a large scale at Lower 
Roxborough, has come to stay, and will, it is believed, ultimately 
become part of all municipal filtration systems. 









3 



Fig. 1.—Lower Roxborough Preliminary Filter House. 







Fig. 2.—Filter House, South Bethlehem, Pa. 










4 


Preliminary filtration in Philadelphia means a practical economy of 
something like twelve or fifteen million dollars. If preliminary filtra¬ 
tion were not resorted to, it would be necessary to expend at least this 
amount of money in building additional sand filters large enough to 
produce, at the old rates, the amount of filtered water required. 

The wat^r supply of South Bethlehem, Pa., drawn from the Lehigh 
River, has been filtered during the last two years by an improved slow 
sand filter plant designed by the author for four million gallons daily. 

The following are the bacterial results: 

South Bethlehem Water Supply. 


Bacterial Analyses of the Water Made under the Authority of Dr. 
Henry S. Drinker, President of the Lehigh University. 


Samples of 

Samples Taken at 

B. Coli. 

Colonies on 
Gelatin Plates. 

1906 

Jan.10. 

Reservoir. 

Present in 1 c.c. 

325 


Filter outlet. 

Not present. 

12 


Tap at University. 

Not present. 

31 

Jan. 17. 

Reservoir. 

Present in 1 c.c. 

650 


! Filter outlet. 

Not present. 

2 


Tap at University. 

j Not present. 

27 

Jan. 24. 

Reservoir. 

Present in 1 c.c. 

1155 


Filter outlet. 

Not present. 

5 


Tap at University. 

Not present. 

53 

March 8. 

Reservoir. 

Present in 1 c.c. 

800 


Filter outlet. 

1 Not present. 

15 


Tap at University. 

Not present. 

32 

March 15. 

Reservoir. 

, Present in 1 c.c. 

150 


Filter outlet. 

Not present. 

14 


Tap at University. 

! Not present. 

33 

March 22. 

Reservoir. 

Present in 1 c.c. 

160 


Filter outlet. 

Not present. 

8 


Tap at University. 

| Not present. 

28 

April 5. 

Reservoir. 

Present in 1 c.c. 

120 


Filter outlet. 

Not present. 

2 


Tap at University. 

Not present. 

16 

May 19. 

Reservoir. 

Present in 1 c.c. 

2209 


Filter outlet. 

Not present. 

9 


Tap at University. 

Not present. 

41 

June 6. 

Reservoir. 

Present in 1 c.c. 

275 


Filter outlet. 

Not present. 

0 


Tap at University.) 

Not present. 

20 

July 16. 

Reservoir. 

Present in'l c.c. 

750 


Filter outlet. 

Not present. 

3 

















































5 


The term “reservoir” here refers to a storage basin in which the 
water remains four or five days on its way from the river to the filter. 

The “tap at the University ” at which the sample was drawn is near 
one of the dead ends of the water-pipe system. The difference be¬ 
tween the water drawn from the “ filter outlet ” and from the “ tap ” is 
explained by the fact that the filtered water passes through an open 
filtered water basin holding two days’ supply. 

The above bacterial analyses were made by Mr. F. W. Green, bacteri¬ 
ologist of the Little Falls (N. J.) filter plant. The samples were taken 
by one of the students of the University and carried by train to Little 
Falls once a week. 

These analyses show three points of interest: 

1. The very low count of bacteria in the filtered water. 

2. The presence of the Bacillus coli in all the samples of raw water 
and its absence in all the samples of filtered water. 

3. The small increase in the number of bacteria found in the filtered 
water drawn at the University. 

The vital record is as satisfactory as the bacterial record. 


Number of Cases and Deaths of Typhoid and Enteric Fever at 
South Bethlehem, Pa. 



1903. 

1904. 

1905. 

1906. 

• 

Cases. 

Deaths. 

Cases. 

Deaths. 

Cases. 

Deaths. 

* Cases. 

Deaths. 

Jan. 

17 

4 

5 

5 

1 

0 

1 

0 

Feb. 

6 

14 

6 

5 

1 

0 

2 

2 

March. 

68 

7 

2 

5 

0 

0 

0 

0 

April. 

66 

12 

8 

2 

0 

0 

1 

1 


157 

37 

21 

17 

2 

0 

4 

3 


Totals. 


1903-1904. 

Before the filter plant 
was installed. * 
Cases. Deaths. 

178 54 


1905-1906. 

After the filter plant 
was installed. 
Cases. Deaths. 

6 3 


The South Bethlehem filter plant consists of six units of scrubbers 
or preliminary filters, 16 feet wide, 38 feet long, 6 feet deep, and six 
units of final filters 16 feet wide, 152 feet long, 6 feet deep. The water 
from the influent gullet enters the bottom of the scrubbers through 


* The filter plant was placed in operation in November, 1904. 































6 


8-inch valves (regulated from the floor over the gullet) and it rises 
upwardly through the scrubbing materials within 6 inches or 8 inches 
of the top of the side division walls and flows naturally to the filter 
beds, which are on the same line, and are only separated from the 
scrubbers by a dwarf wall. When in normal operation, the level of the 
water on the scrubbers and on the filters is the same, and there is 
practically no motion on the surface. 

In the final filters the water flows downward, in the usual way, through 
the filtering materials, and comes out into the effluent gallery, which is 



Fig. 3.—Interior View of the South Bethlehem Filter Plant. 


six feet deep, through 8-inch valves which are always submerged in 
water. Provision is made at the end of each filtered water outlet for 
wasting the first filtered water through a 6-inch valve, attached to a 
pipe connected with the different filter units, and allowing also back 
filling with filtered water. 

The division and end walls, as well as the floors of the scrubbers and 
final filters, are constructed of concrete reinforced throughout with 
half-inch square iron bars. 

Over the filtered water gallery is a reinforced concrete floor through 


\ 




7 


which the stems of the effluent valves and re-wash valves pass. These 
stems are supported by indicator stands, which help to regulate the 
flow of filtered water. This space may be called the gate chamber. 
There is plenty of room for the manipulation of the valves, the reading 
of the loss of head gauges and the sampling of each filter unit. 

One of the features of the South Bethlehem plant is the cleaning 
operation. A yellow pine coping is laid on the division walls and flat 
steel rails are set thereon. A crane travels on these rails and an 



Fig. 4.—Valve Gallery, South Bethlehem Filter Plant. 


arrangement is made for the transfer of the crane from one bed to the 
other. 

The crane is used for the following purposes: 

1. A platform attached to the crane is lowered close to the sand- 
bed for the collection of the dirty sand and it is raised for transfer 
from one filter unit to the other. The man who scrapes the sand stands 
on the platform, and when the platform is loaded, the crane is pushed 
toward the sand washer by men walking on the division walls, so that 
at no time have the men to set foot on the sand-bed itself. The same 
device is used to receive the clean sand and distribute it over the bed. 












8 


2. The crane and platform are also used to level or plane the sand 
layer after it is replaced on the bed. 

3. A trough erected on the crane is used for the distribution of the 
artificial filtering membrane. 

The sand washer used at South Bethlehem was designed by the 
author and constructed by the Link Belt Co. It consists of four bucket 
elevators with suitable framework, shafting, countershafting, and a 
trough. It is operated with an electro-motor which is' also used for 



Fig. 5.—Crane and Platform to Receive and Carry the Dirty Sand to 
the Washing Apparatus, to Convey the Clean Sand Back to the Bed 
and to Plane the Surface after Resanding; South Bethleh\m Fil¬ 
ter Plant. 


the sponge-washing machinery. The sand-washing machine and the 
sponge-washing machine are erected on platforms which are moved on 
the “I” beams of the scrubber close to the filter in process of cleaning. 
The crane and platform bring the dirty sand to the washer, it is shoveled 
fiom the platform into a boot not more than two feet high, where it is 
taken up by the first elevator. It is raised some nine feet in the air and 
then made to drop with a certain force into the water of the trough 
below; the sand is taken up again by the second elevator, raised and 







9 


dropped in the water as before; it is lifted a third time and again 
thrown in the water; the fourth and last time it is raised from the 
washing trough and falls in a chute which leads the clean sand to the 
traveling crane for distribution on the bed. In this process each particle 
of sand comes in direct contact, more or less violent, with the water 
which it strikes; it is freed from mud by the force of impact. The 
sand is handled in very small quantities at a time, is not subject to 
the law of currents, and never forms any stratification. 

The wash water enters in the trough from the far end which receives 



Fig. 6.—Sand Washer, South Bethlehem Filter Plant. 


the clean sand and goes out at the near end which receives the dirty 
sand. The flow is regulated so as not to carry away any of the fine 
sand. 

The following are some of the advantages of this new system: 

1. Very little water is required, it need not be filtered water, nor has 
it to be under pressure. 

2. The sand is washed as soon as scraped without remaining in 
heaps, in courts, exposed to wind, rain, frost, dust, etc. 

3. The sand being washed fresh, the mud comes off easily, and being 














10 


replaced on the bed as soon as washed, the filtering layer is always 
of the same thickness. 

4. The sand is at no time stratified, as is the case with the ordinary 
methods of washing. 

5. Nor is there at any time any waste or separation of the finer 
particles of sand, which are absolutely necessary to produce good 
filtration. By the ordinary system of washing sand, there is consider¬ 
able separation of the different sizes of particles, according to their 
specific gravity, and much waste of the finest particles; this renders 
the efficiency of the filter less and less after each cleaning. With the 
system inangurated at South Bethlehem, the physical condition of 
the sand is always the same. 

Among the novel features of the South Bethlehem filter plant as a 
slow sand filter are: 

1. Light and well ventilated filter house. 

2. Narrow filter beds and comparatively small units. One-eighteenth 
of an acre instead of the usual large units of half, three-quarter, or 
whole acre. 

3. Shallow layer of water over the sand-bed showing the possibility 
of reducing the height of the filter walls to a minimum. 

4. Cleaning without trampling on the sand. 

5. Washing the sand without losing the fine particles or separating 
it in different grades. 

6. Avoiding sand courts with the waste and pollution resulting from 
exposure. 

7. High speed of filtration—from six to nine million gallons per 
acre, per day, right from the start. 

8. Long runs of three months or more without scraping. 

9. Facilities for distributing and removing the filtering materials, 
and forming the artificial membrane. 

10. Compactness, simplicity, and easy control of the whole plant. 

11. No constant labor of any kind, the attendant hitherto in charge 
of the reservoirs attends to the filters. When a cleaning operation is 
necessary, it is carried on by the ordinary staff of the water company. 

12. The mechanical power required for all the washing operations is 
supplied by a 5 H. P. electrical motor. 

At the St. Louis Convention of the American Society of Civil Engineers, 
in 1904, the author was asked if he had any information as to the effect 
of storing filtered water in open reservoirs, and he had to acknowledge, 
at the time, that he had none. Now he has had two years’ experience 


11 


at Bethlehem, Pa., nine months at Lancaster, Pa., and nearly two 
two years at Kittanning, Pa. In no case has he found the filtered 
water seriously affected by exposure. 

No doubt some germs fall into open reservoirs with the dust of the 
air, with the leaves, and in various other ways, but they do not seem 
to multiply to any great extent. Is it because the filtered water does 
not contain more than a trace of organic matter? Is it because the 
sunlight checks their growth or kills the adult bacteria? We do not 
know. 

The very small increase in the number of bacteria found in the water 
drawn from the town pipes as compared with those in the water col¬ 
lected direct from the filters, is very interesting, particularly when we 
think of the precautions considered necessary in collecting and trans¬ 
porting samples of water for bacterial examination. 

With the present information the author sees no objection to the 
storage of filtered water in open reservoirs, provided, of course, care 
be taken to prevent dirt of every description, dogs, and would-be 
suicides getting into them. It would be very much better to have a 
large open reservoir able to compensate fully for the difference in the 
consumption at different hours of the day and night, without changing 
the rates of filtration, than to have a small covered reservoir with 
which it w’ould be necessary to change the rate of filtration several 
times a-day to respond to the ever varying demand of consumption. 

The city of Lancaster, Pa., is supplied with water drawn from the 
Conestoga River. It is filtered by an improved slow sand filter plant 
designed by the writer and is intended to purify nine million gallons 
of water daily. It was placed in operation in April, 1906. The bac¬ 
terial and turbidity record is given on page 13. 

The samples were brought from Lancaster to Philadelphia and were 
planted from six to twenty-four hours after being drawn. They were 
read forty-eight or seventy-two hours after planting. 

Fig. 7 shows the general view of the Lancaster filter plant in use 
before the roof was put on. This filter plant has several features of 
special interest: 

I. There is no storage or settling reservoir. The water is pumped 
direct from the river to the filters all the time, day and night, whether it 
be roily or not. 

There were last summer seventy-five thunder-storms, and after each 
storm the river rose, and much loam, clay, and vegetable detritus 
made the water extremely muddy. To meet this special condition the 


12 


writer designed and installed, in addition to the improved slow sand 
filter, a system of chemical purification along the lines of his water 
softening system, which is largely used in England for the purification 
of hard (drinking) water. 

In this system the reagents are used in a dry powdered form. The 
powder is placed in hoppers from which blades expel it through sliding 
doors opened more or less according to the requirements of the water. 
The incoming water is made to impinge upon,an undershot water 



Fig. 7. —Lancaster Filter Plant in Use before being Covered. 


wheel of the Poncelot type, and the force thus obtained is sufficient not 
only to expel the powder from the hoppers but also to stir up the water 
in which the powder falls, so that there is a thorough mixing of the 
reagents with the water. 

The quantity of powder is proportioned to the quantity of incoming 
water. If the water comes to the wheel fast, the hoppers deliver the 
powder fast; if the water comes slowly, the powder is supplied slowly 
to the water; and if there is a complete stop of the water, there is also 
a complete stop in the supply of the powder. 




13 


The success of this feature is absolute. More than four hundred in¬ 
stallations have been made and maintained in England for many 
years, for softening the water coming into houses, mansions, and public 
institutions, and there has never been a failure. Water-softening 
processes in which the reagents are used in a liquid form have all failed 
more or less at some time or other because of the practical impossibility 
of securing regularity in the proportionate feed of the reagents. 


City of Lancaster Water Supply. 

Bacterial and Ttirbidity Record of the Filter Plant. Analyses 
made by Dr. W. J. Dugan, Bacteriologist. 


Date. 

Bacteria. 

i 

Per Cent. 

Turbidity 

Effluent. 

Raw Water. 

Gen. Effluent. 

Removed. 

Parts per 
Million. 

1906. 

April 16. 

3,800 

69 

98.18 

3 

18. 

5,400 

66 

98.96 

1 

24. 

4,300 

32 

99.30 

1 

26. 

3,200 

26 

99.25 

1 

May 8. 

5,300 

69 

97.7 

0.0 

20. 

7,600 

69 

98.94 

0.5 

24. 

5,700 

86 

98.50 


June 1. 

9,800 

78 

99.18 

1 ’ 

6. 

10,200 

80 

99.22 

0.0 

8. 

3,600 

65 

98.47 

1 

11. 

4,100 

36 

99.11 

0.5 

15. 

3,300 

25 

99.24 

0.5 

21. 

11,600 

90 

99.20 

0.5 

26. 

8,040 

63 

99.22 

0.0 

28. 

11,760 

75 

99.36 


July 5 . 

5,630 

23 

99.59 

6.5 

12. 

6,970 

59 

99.15 

0.0 

18. 

12,300 

93 

99.24 

1 

19. 

8,970 

61 

99.32 

0.5 

24. 

18,400 

59 

99.68 

0.5 

26. 

12,200 



0.0 

Aug. 1. 

5,690 

io 

99.82 

0.0 

3. 

4,380 

40 

99.09 

0.5 

7. 

* 5,360 

12 

99.64 

0.5 

9. 

8,390 

79 

99.07 


14. 

4,670 

14 

99.70 

6.5 

16. 

8,690 

60 

99.31 

0.0 

21..... . 

6,280 

17 

99.73 

0.0 

24. 

16,300 

46 

99.72 

0.0 

28. ! 

8,360 

28 

99.81 

0.0 

30. 

7,630 

21 

99.72 

0.0 

Sept. 5. 

5,600 

21 

99.63 

0.0 

6.. .*... 

6,180 

31 

99.34 

.. 

10. 

3,300 

15 

99.55 

.. 

17. 

6,780 

43 

99.37 

0.0 
























































14 


After receiving the desired quantity of reagents (at Lancaster) the 
water passes into a circular tank 50 feet in diameter, 10 feet deep, with 
three concentric baffle-walls which help to further agitate the water, 
then through another tank of the same size with one baffle wall. The 
water settles in this latter tank and it finally passes into two other 
tanks of the same size but at the bottom of which there is a series of 
layers of coarse scrubbing materials, stone, coke, and sponge. After 
leaving these two tanks the water is in a very good state of preparedness 
for filtration. 

At first the reagents used at Lancaster were principally lime and soda, 



Fig. 8.—Interior View of the Lancaster Filter Plant. 


with a view of softening the water, but as it was considered desirable 
not to change the chemical character of the water in any way whatso¬ 
ever, sulphate of alumina and soda carbonate are now used. These 
two reagents neutralize each other. They simply coagulate the fine 
suspended matter without making the water harder or softer and with¬ 
out leaving anything objectionable in it. The water is never more 
acid nor more alkaline after treatment than before. 

This process is, of course, more expensive than that in which sulphate 
of alumina or alum alone is used, but it is more satisfactory. It is 



15 


folly to trifle with the health of the people for economy’s sake; we 
must purify the water and not make it worse (as is the case when 
sulphate of alumina or alum alone is used). 

The water thus prepared now goes to the filter system proper, which 
is composed of fifteen scrubbers (or preliminary filter units) 35 feet 
long, 16 feet wide, 6 feet deep, and fifteen final slow sand filters, 140 
feet long, 16 feet wide, 6 feet deep. Each filter unit is therefore 2240 
square feet, or about -fo acre. 

The materials used in the scrubbers, beginning from the bottom are: 

1. A 9-inch layer of 3-inch pebble stones. 

2. A 9-inch layer of coke, “stove” size. 

3. Twenty-four inches of space is occupied by four rows of slates 
placed at a slight angle upwardly, each row in a contrary direction, so 
that the water in its upward flow is compelled to take a circuitous or 
spiral course. The space between the slates is filled with coke “nut” 
size. 

4. An 18-inch layer of sponge, held down by cedar slats, yellow pine 
stringers, wood blocks, and steel “I” beams fastened on the walls. 

The drainage system in the sand-beds or final filters is similar to that 
of the scrubbers. It consists of convex slabs made of concrete, with 
openings at the base. These slabs are laid in the center of the bed 
whose floor is dished. A perfect drainage is thus secured and no 
stagna-nt water can remain in any part of the filter bed. 

The materials used in the final filters, beginning from the bottom are: 

1. Eighteen inches of gravel, graded from 3 inches to ^ inch. 

2. Two feet of filter sand. 

II. The second feature of interest—employed also at the South 
Bethlehem plant—is the formation of an artificial filtering membrane 
on the surface of the sand layer. It has been said that a sand filter is 
not good unless it has on the surface what has been called an “ algean 
jelly,” a “Schmutzdecke” (mud blanket), or a “biological” filtering 
membrane. There is in this statement a grain of truth and a mountain 
of fiction. The grain of truth is that the accumulation of particles of 
very fine suspended matter, organic and inorganic, on and between the 
grains of sand, fills the voids and increases the density of the sand layer. 
In other words it makes a physically finer filter. 

The idea concerning the “algean jelly” had its origin in Europe, 
where the filters are usually uncovered and in which algae grow on the 
sand under the influence of sunlight. 

Algae do not grow in covered filters and if their presence were neces- 


16 


sary to good filtration their absence in covered filters would lead to 
bad results, which is not the case. 

The existence of a natural “ Schmutzdecke ” coincides with the better 
physical condition of the sand layer, the improvement in the filtrate 
is not proportionate to the thickness of the mud. It may be said, 
however, that the increase in mud, as we shall see later on, does not 
tend to make the filter worse; if anything it makes it better. 

The promoters of the “biological” idea would have us believe that 
there are accumulated on the sand bed cannibal-like bacteria whose 
propensity is to eat their weaker brethren. This is pure romance! 



Fig. 9.—Lancaster Filter Plant and Pure Water Reservoir. 


The fact, however, remains that the natural or artificial deposition of 
fine particles of suspended matter on the sand is a decided advantage. 
In the operation of the plain slow sand filters in which there is nothing 
but a natural or mud membrane, the filters are started first at 0.5 mil¬ 
lion gallons per acre per day and kept at this rate for several days, then 
the speed is increased to 1, 1J, 2, 2\, and sometimes 3 million gallons 
per acre per day! 

It occurred to the writer.that instead of trusting to the slowly formed 





17 


and delicate natural “Schmutzdecke” it would be better to deposit 
on the sand layer at the beginning of the operation a film of finely 
divided inorganic matter. This has been done with success at South 
Bethlehem and Lancaster and the filters are started at full rates— 
6, 8, or 9 million gallons per acre per day. 

Some years ago the writer advocated using asbestos fiber for the 
artificial filtering membrane. He used it at South Bethlehem, but has 
found that equally good results could be obtained with fine charcoal 



Fig. 10.—Lancaster Filters, before being Covered. Algas Growth in 
the Near Bed, no Algas in the Far Bed. 


and fine coke. Coke is that which is now used at South Bethlehem and 
Lancaster. 

After passing through the filtering system the purified water goes 
into an open pure water reservoir built of reinforced concrete, 200 feet 
long, 100 feet wide, 12 feet deep, having a total capacity of about 
1,500,000 gallons. 

The effluent pipes are so arranged that the reservoir can be emptied 
at any time for cleaning. When this is done the filtered water goes 
directly from the filters to the high duty pumps. 

2 












18 


There is quite a difference of opinion among filtration men as to the 
best depth of underdraining materials. In London, for instance, 30 
inches is the accepted thickness; in Berlin 33 inches. Some engineers 
in this country think 12 inches enough. The author prefers 18 inches. 

Fig. 10 shows a curious phenomenon well worthy of attention. One 
of the filter units presents a spotless sheet of water. In the other are 
to be seen dark spots on the surface of the water and against the filter 
wall. This represents green algae. Out of fourteen filter beds in use 
at the time seven had this growth, and the other seven had none what¬ 
ever. The applied water was the same; the exposure the same; the 
period of time in use the same. The only difference between the two 
was that in the filters which had no algae the sand was covered by a 
thin coating of powdered coke, while in the other the sand was bare, 
and it was on the bare sand that the algae took root and grew in a few 
days so as to cover the whole surface of the beds like a diminutive 
forest of pine trees. In some of the beds in which the coke was placed 
some parts of the black filtering membrane were removed so as to ex¬ 
pose the sand, and immediately within a day or two algae grew in 
those parts. 

We state the fact but cannot offer any explanation. Had the black 
color of the coke any specific role in thwarting the fertilizing influence of 
the sun’s rays, or was it the coke itself which was incapable of support¬ 
ing vegetable life? In considering the latter supposition we should 
bear in mind that there were only 300 pounds of very finely divided 
coke distributed over 2240 square feet of surface. The layer was cer¬ 
tainly not more than inch thick. 

The theory of the black color would appear to be supported by an 
observation made at South Bethlehem. The pure water basin is 
lined with riprap stones. These stones were habitually black, owing 
to the soot of the locomotives (of the Lehigh Railway) falling into the 
reservoir. No trouble had ever been experienced before, but this 
summer, in order to show off the transparency of the filtered water, 
the superintendent of the filter plant had the idea of whitewashing the 
stones some 4 feet below the flow line, and sure enough there soon came 
a very luxuriant growth of algae on the white stones. Since the stones 
have become black again the algae have not made their appearance. 

Sand filtration is supposed to be a natural process—an imitation of 
nature, but it is not so. Nature’s sand is never disturbed; it is never 
taken out and washed; no dirt ever comes in contact with it. When 
the water gets to the sand in nature it has long before been clarified or 


19 


scrubbed by leaves, roots, debris, loam, gravel, etc. Nature’s sand is 
not confined between walls. It has thousands of acres to do its work. 

When any one says that a process is like that of nature, no further 
explanation or proof is asked. “Of course if it is natural it must be 
good!” But what is known as a plain slow sand filter has very little 
in common with nature. It may even be said that there is very little 
engineering science or art about it. 

Dr. Kemna, of Antwerp, describes a plain slow sand filter as fol¬ 
lows: “A heap of sand—water is put on the top and extracted from 
underneath. It is worked by a foreman who knows, of course, how 
much water he pumps on the filters but who cannot always tell how 
much each particular filter is doing, its speed, etc. Generally the 
filters are left to settle that between themselves.” 

Referring to certain undesirable features in certain plain slow sand 
filter plants, a young friend of the writer described the system as “a 
lot of sand in water.” 

In some cases the sand is not compact enough to make a good 
strainer. It behaves somewhat like quicksand, offering practically 
no resistance to the flow of the water. The sand itself may be too 
coarse or too uniform—that is, not containing enough fine particles 
to make up a fine screen—or again it may have fissures, breaks, or free 
passages. These occur particularly along the retaining walls or pillars, 
so that sometimes the filtering operation is defective. 

It is time that students of the art of filtration should cease to merely 
copy what has been done abroad. They know nothing of the secret 
failures of these foreign plants; they know only the good that is said of 
them in books. It is time that they should make some original study 
as to how best to do the work and not how cheaply. 

The South Bethlehem and Lancaster plants are object lessons. The 
members of this Club will be heartily welcomed if they visit them. 
They will be given full information concerning every detail of con¬ 
struction and operation. They will see new systems of washing the 
sand in the bed and out of the bed, new ways of scraping and planing 
the sand, methods of washing the sponge and coke, and many other 
new features. 


Mechanical Filters. 

Mechanical filtration is carried on in tanks seldom larger than 20 
feet in diameter; sulphate of alumina is added to the water, the small 
particles of sediment are coagulated and aggregated into comparatively 


20 


coarse particles which are easily arrested by coarse sand, and thus it is 
that very high rates of filtration, from 80 to 120 million gallons per 
acre per day, are obtained. 

Filters do not clog according to the quantity of water which goes 
through them, but according to the quantity of suspended matter 
floating in the water. The so-called mechanical or rapid filters must 
be cleaned more often than the slow sand filters. The cleaning opera¬ 
tion is ordinarily done two or three times a day, and, when the water 
is very bad, every few hours. 

This is done by introducing water under pressure below the sand 
layer and agitating the sand mechanically with rakes (hence the name 
mechanical filtration), or by blowing air backward through the sand 
layer. In other words, the sand is agitated in the tank itself, and the 
impurities are supposed to be removed by the overflowing wash water. 

The hygienic results are not always satisfactory. Mechanical filters 
have been installed in many small cities because the rate of filtration 
is so high that the size of the plant is comparatively small and propor¬ 
tionately cheap in first cost; but the cost of operation and mainte¬ 
nance is much greater than that of slow sand filters. 

The principal defects of this system are: 

1. The necessity for constant care and attention day and night to 
adjust the chemicals to the varying conditions of the water and to 
attend to the cleaning operation. 

2. The cost of chemicals. 

3. The increased amount of incrustating constituents in the water. 

4. The frequent disturbance of the sand for cleaning—the worst of 
all. 

Dr. Med. Karl Schreiber, of Berlin, in a report on mechanical filtra¬ 
tion, considers that “the effluent may be turned to use after half an 
hour,” and he adds: “At times of epidemics, when the raw water is 
suspected of being infected, it might be well to extend this period to 
one hour after the commencement of the run.” 

The advice given by some engineers to the effect that this first water 
should not be wasted would thus appear to be unwise. They say “the 
small quantity of impurities coming from one unit out of many would 
not lower the general efficiency to any very great extent.” It may be 
so, but the author would not like to be a party to such a saving! 

The following table shows the work done by mechanical filters 
immediately after cleaning, and the necessity of wasting the filtered 
water during the first half-hour of operation: 


21 



Bacteria in 

Bacteria in 

Time. 

Raw Water 

Filtered Water 

Per c.c. 

Per c.c. 

10 A.M.. 

. . ..900 

(immediately before washing) 116 

10.50 “ . 


(filtering started at 10.40) 1900 

11.50 “ . 


3200 

11.20 “ . 

C( 

510 

11.40 “ . 

a 

36 

11.50 “ . 

u 

80 

3.30 P.M.. 

(( 

42 

4.40 “ . 

... . “ 

4800 

6 “ .“ 

Stopped for washing. 

22 

11.40 A.M.. 

.... 5200 

(filtering started) 34000 

11.45 . 


30000 

11.50 “ . 

U 

6400 

12 M. . 

u 

1540 

12.5 P.M... 

u 

895 

12.10 “ . 

(( 

248 

2.35 “ . 

. ... " 

52 

4.00 “ . 

(C 

38 

4.50 “ . “ 

Stopped for washing. 

42 


Domestic Water Supply. 

Are domestic filters a “delusion and a snare” or are they desirable 
utensils ? 

The question cannot be allowed to remain in doubt. If they are 
bad they should be condemned and thrown out of existence altogether. 
If they are good they should be used and cherished. The fact that a 
filter is small or large does not make it either good or bad. If there are 
good big filters, why should there not be good small filters? 

Let us study a few of the principles which obtain in the art of filtra¬ 
tion as now practised. We may perhaps find out whether there can 
be any good filters and whether it is possible to distinguish between 
good, bad, and indifferent filters. 

The United States Patent Office classes water filters in two cate¬ 
gories : 

1. Porous wall filters. 

2. Granular bed filters. 


Porous Wall Filters. 

The most representative specimen of this kind of filter is that made 
of unglazed porcelain. The pores or channels through which the water 
has to pass are “fixed” or “rigid.” There is no “give and take,” as 
in the loose material of granular beds. If the bacteria or their spores 
pass the surface openings of these fixed channels there is nothing be- 





















22 

yond to prevent them passing or growing right through the thin walls. 
In fact, this has been found to be the case. 

M. Armand Gautier (“Encyclopedic d’Hygiene,” Paris, 1890), says: 
“The colonies (of bacteria), at first retained on the surface, grow in and 
through the pores of the porcelain. . . . This has been confirmed 

by MM. Gallipe and Villejean.” 

The “Lyon Medical” (July 15, 1888) says: “The microbes that 
have succeeded in going through (the pores of the porcelain) grow 
therein. . . . Unless we tested daily the ‘ candles’ we would not 

dare to use the water for washing wounds.” 

M. Lacour (“Revue d’Hygiene,” June 20,1892) says: “After a year’s 
experience . . . the following is the average result: 

Filtered water of the first day.Sterile. 

Filtered water of the second day. . .Sterile. 

Filtered water of the third day.Some germs similar to those in 

the applied water. 

Filtered water of the fourth day... Colonies in increased number. 

Filtered water of the fifth day.Quantity three, four, five, and 

six times greater than those 
of the unfiltered water.” 

M. Miquel (Report to the Paris Municipal Council, Dec. 3, 1892): 
“The bacteria may traverse the porcelain filter by multiplying in the 
pores of the filtering material and grow through in a more or less long 
period of time.” 

Dr. Chaltin (“Archives Medicales Beiges,” May, 1894)—summary 
of experiments: 


First day. 4 colonies. 

Third day. 130 colonies. 

Sixth day. 460 colonies. 

Eighth day. 780 colonies. 

Tenth day.1600 colonies. 

The unfiltered water contained. 50 colonies. 


Dr. Odo Budwig (Paris Congress of Hygiene): “Unfiltered water 
containing 200 or 300 colonies comes out of porcelain filters with 60,000 
or 70,000.” 

The “Revue Scientifique,” Paris (July 13, 1889): “The porcelain 
filter which, the first days that follow its sterilization, gives water 
without microbes, gets soon infected, and allows bacteria to pass. It 
may be a very good laboratory filter, where apparatus for sterilizing 
is always at hand, and where ‘candles’ may be at any moment ster¬ 
ilized by superheated steam; but in houses, as a private hygienic in¬ 
strument, it is a detestable filter. 


i 











23 


“ It is evident that persons who have got one fixed up in their kitchen 
or pantry will not get it down every week to replace the ‘ candle ; by a 
new one or by one freshly sterilized; then, after a few days, the water 
that such persons drink is, so far as microbes are concerned, not better 
than that of those who have no filter at all. The danger is all the 
greater that, on the faith of the assertions of the authors and of the 
prospectus, such persons as use it have perfect confidence in it 
This must be said to the public—allowing it to be misled on this sub¬ 
ject would deserve to be severely judged.” 

The conclusion to be drawn from these quotations is that “ porous 
wall ” filters must be cleaned 'and sterilized by heat very often. 

Granular Bed Filters. 

The best type of “granular” bed filters is that known as “the slow 
sand filter” used for the purification of city water supplies. In a well 
constructed and carefully operated slow sand filter the bacteria are 
retained, with the particles of inert matter, in the voids between the 
grains, mostly at the surface of the sand layer. 

These voids may be compared to cells. Some of the bacteria which 
fail to remain in the upper cells are in part retained in the cells below. 
The number of bacteria to be found in the lower layers of sand or left 
in the water as it progresses downward through the sand becomes 
gradually smaller and smaller, until at the bottom the sand and the 
water are practically free from bacteria. 

On examining bacteriologically the different sections of a normal 
sand bed in use for some time—say six months or more—you may find 
millions of bacteria in a gramme of sand taken at the surface; an inch 
below a few thousand, and several inches below hundreds only; at the 
bottom hardly any; and those few may be of a kind which is not in the 
applied water. 

Water bacteria retained in granular bed filters do not, in the opinion 
of the writer, multiply. They accumulate and ultimately die. Some 
go through the term of their natural life and cease to live; others are, as 
it were, smothered by the mass of inorganic matter in which they are 
entangled, and others again practically starve. 

The notion that the accumulation of mud in filters is to be depre¬ 
cated, that the bacteria grow and multiply in the mud, and that the 
filtering materials should be changed or kept clean all the time, is a 
mistake. This is proved by the behavior of the slow sand filters, which 
always improve with age, a fact that has strongly impressed the writer 


24 


as the result of over ten thousand analyses made during the last nine 
years, not only with sand filters but with scrubbers also, at his testing 
station on Arch street, at Lower Roxborough, at South' Bethlehem, 
Lancaster, and elsewhere. 

Take as illustration a test made by Dr. W. J. Dugan in the writer’s 
laboratory. 

A small piece of sponge was carefully taken with sterilized forceps 
out of a preliminary filter or scrubber which had been in use three 
months. It was washed in sterilized water. The wash water was 
tested for bacteria. The piece of sponge when dry weighed 1 gramme. 
By estimating the number of bacteria which were in the water before 
and after passing through one gramme of sponge, we had: 

Bacteria in the applied water.40,000,000 

Bacteria in the scrubbed water. 8,000,000 

Bacteria in the sponge. 37,000 

Bacteria which had died in the sponge... . 31,000,000 40,000,000 


In not a single case in all our experiments did we ever find the water 
coming out of the scrubbers worse than the applied water, although 
scrubbing materials were in some cases saturated with mud. On the 
contrary, it has always been found bacteriologically better by 50, 60, 
70, 80, and sometimes 90 per cent. 

It is well known that typhoid bacilli die in water in less than fifteen 
days, whether the water contains other bacteria or not. Thus, for 
instance, Prof. Ray Lankester of Oxford (England) made “a strong 
preparation of typhoid bacilli and introduced it in distilled water.” 
During five consecutive days a liter of this polluted water was each 
day put in a Maignen filter, with the following results: 

The Water Contained 


Typhoid Colonies. Before Filtration. After Filtration. 

First day.300,000 0 

Second day. 11,000 0 

Third day. 3,000 0 

Fourth day. 1,000 0 

Fifth day. 66 0 


The number of colonies in the water before filtration, as thus shown, 
became less and less every day, though nothing was done to the water. 
The bacilli simply died. None of the bacteria are eternal, nor is their 
growth without limit. The spores, or bacteria, if kept dry, may retain 
their latent principle of life indefinitely, like a grain of wheat in a 
granary, but as soon as these spores or dry germs are introduced into 











25 


water or placed in a moist environment, they sprout or come to active 
life, and after a time, as the rest of animated creation, they die. Some¬ 
times their destruction is due to a kind of auto-intoxication. Thus, 
for instance, take a gelatin plate which has been planted with water 
containing bacteria; you will find some colonies very small, some 
large, and others larger still. It may be asked why does not a single 
colony cover the whole plate? Why does the growth of the colony stop 
at any given diameter. In the absence of any other explanation we 
are left to imagine that the soluble products of bacterial metabolism 
have poisoned the environment and prevented further growth, as 
carbonic acid would asphyxiate us if the air that we breathe were not 
renewed. 

When the colonies have reached a certain point of multiplication 
they do not grow any more unless they are transplanted into fresh cul¬ 
tures. There are some bacteria which liquefy the gelatin and produce 
gas; these may in time spread over the whole plate, but those which are 
non-liquefying appear to have a well-defined self-inhibiting limit. 

Some writers have affirmed that the so-called process of “ripening” 
fitters consists in the growth, in the voids between the grains of sand and 
on their surface, of “beneficent” bacteria which are supposed to de¬ 
stroy the “maleficent” ones. This is pure romance. There is on the 
sand an accumulation of bacteria from the ever-increasing quantity of 
water passed through the filter. These are neither eating nor being 
eaten, they simply die, that is all! 

Charcoal. 

Charcoal has been praised by some and condemned by others. Those 
who have condemned it have not gone far enough in their investigation. 
It has been asserted that charcoal is favorable to the growth of micro¬ 
organisms. This statement, which has gained credence in Europe, is 
based upon an error which the writer will now attempt to explain. 

The first attack made on charcoal as a filtering medium appeared in a 
book entitled “Micro-organisms in Water.” Under the heading, 
“Efficiency of Different Filtering Materials” (Percy Frarikland, 1885), 
we find the following table on page 26. 

On examining this table, one would naturally suppose that an acci¬ 
dent had occurred to the charcoal filter in the last test. In any case 
such a single result cannot justify any conclusion and much less the 
condemnation of charcoal as a filtering material! 


26 




Filtering 

Material. 


Micro-organisms per c.c. 

Reduc¬ 

tion 

Approximate 
Rate, of Fil¬ 

Efficiency. 

Unfiltered 

Water. 

Filtered 

Water. 

per 

Cent. 

tration PER 
•Square Foot 
per Hour. 

Iron sponge. 

Initial test. 

o 

00 

0 

100.0 


After 12 days’ ac¬ 
tion . 

2800 

0 

100.0 

0.40 gals. 


After 1 month’s 
action. 

1280 

2 

99.8 

0.45 gals. 

Animal 
charcoal.. 

Initial test. 

After 12 days’ 
action. 

Too nu¬ 
merous 
to count. 

2800 

o o 

100.0 

100.0 

0.46 gals. 


After 1 month’s 
action. 

1280 

1000 

447.0 

0.86 gals. 



_ 


Increase 



Four questions present themselves here: 

1. How is it that the water applied to the iron in the initial test was 
different from that applied to the charcoal? In the first case there 
were only eighty bacteria in the applied water; in the second, the bac¬ 
teria were “ too numerous to count.” The applied water ought to have 
been the same in both initial tests. 

2. Why was the speed of filtration in the animal charcoal filter in 
the third test allowed to be nearly twice as great as in the other tests ? 

3. Were the filters kept working every day, all day and all night, 
during 30 days, or were they working only on the 1st, the 12th, and on 
the last day of the month, and for how many hours at a time? 

4. Was the charcoal left undisturbed during all the test period? 

Is charcoal favorable to the growth of micro-organisms? 

In order to find out what truth or error there was in the assertion 
that animal charcoal was favorable to the growth of micro-organisms, 
the writer undertook a series of experiments which lasted a full year. 

The premises were: 

1. Take the animal charcoal as it is used in filters. 

2. Apply water containing as few bacteria as possible in order to 
avoid the error of counting, as water germs, the air germs that were in 
the charcoal before use. 

3. Do not submit the charcoal to any kind of artificial sterilization, 
but test it in the laboratory as it is used in daily practice. 
































27 


Bacteriological Test of Charcoal. 

Made in the Writer’s Laboratory by Dr. W. J. Dugan, Bacteriologist. 

We took three glass laboratory percolators containing about 100 
cubic inches each and placed therein about 80 cubic inches of char¬ 
coal (carbo-calcis), and passed water daily, Sundays excepted, during 
fourteen weeks. Neither percolator nor charcoal was sterilized in any 
way. The examinations of the plates were made three, four, or five 
days after the cultures were prepared. The cultures were made in 
Petrie’s dishes with the ordinary gelatin medium. Note was taken of 
the number of liquefying bacteria before and after filtration. 

The following are the results: 






Water Filtered through Carbo-calcis. 

.Dates. 

Water Used. 

Filter No. 1. 

Filter No. 2. 

Filter No. 3. 

Sampling. 

Examination. 

Total number of 
bacteria per c.c. 

' 1 

Liquefying. 

Total number of 
bacteria per c.c. 

Liquefying. 

Total number of 
bacteria per c.c. 

Liquefying. 

Total number of 
bacteria per c.c. 

Liquefying. 

1900 

Sept. 8.. 

Sept. 13 

36 

8 

412 

12 

300 

24 

620 

16 

10. .. 

15 

32 

8 

360 

10 

276 

18 

520 

16 

11.. . 

15 

28 

8 

316 

8 

240 

14 

460 

20 

12.. . 

16 

18 

0 

3 ; 720 

30 

3,360 

20 

3,420 

24 

13. . . 

16 

16 

0 

4,140 

10 

4,224 

8 

3,700 

0 

14. . . 

19 

18 

6 

5,600 

0 

9,000 

0 

6,120 

16 

15. . . 

20 

16 

4 

4,800 

0 

7,740 

0 

5,720 

0 

17. . . 

22 

22 

4 

4,500 

0 

6,480 

0 

5,340 

0 . 

19.. . 

22 

16 

6 

4,160 

0 

5,940 

0 

4,640 

0 

20.. . 

23 

28 

10 

3,920 

0 

4,860 

0 

4,180 

0 

21. 

26 

34 

12 

3,064 

0 

4,388 

0 

3,358 

0 

22... 

27 

16 

4 

2,677 

0 

3,346 

0 

2,534 

0 

24... 

28 

20 

4 

2,326 

10 

2,634 

8 

2,196 

14 

25... 

29 

14 

0 

2,032 

6 

2,216 

0 

1,968 

16 

26... 

29 

120 

44 

1,800 

0 

2.098 

12 

1,920 

16 

27... 

Oct. 2 

84 

16 

1,660 

0 

2,430 

30 

1,808 

18 

28. 

2 

36 

18 

1,560 

0 

2,180 

8 

1 620 

2 

29! 

3 

16 

0 

1,500 

0 

2,032 

6 

1,520 

0 

Oct. 1. . . 

4 

16 

2 

1,250 

0 

1,460 

0 

1,280 

6 

3... 

6 

18 

0 

1,060 

0 

1,200 

0 

1,040 

0 

A.. . 

10 

18 

4 

980 

0 

1,120 

0 

990 

0 

5. .. 

10 

1,048 

46 

926 

12 

1,076 

8 

910 

2 

6... 

9 

16 

0 

624 

0 

1,060 

16 

740 

0 

8 . ’ 

11 

16 

0 

60 

0 

180 

0 

36 

0 

9.. . 

13 

26 

0 

40 

0 

190 

0 

16 

0 

10. 

14 

28 

0 

16 

0 

80 

0 

14 

0 

11.. . 

15 

26 

0 

10 

0 

18 

0 

14 

0 

12 ... 

16 

8 

0 

4 

0 

2 

0 

8 

0 

13!!! 

17 

10 

0 

0 

0 

0 

0 

4 

0 

15. 

19 

8 

0 

0 

0 

0 

0 

4 

0 

16!!! 

20 

10 

0 

0 

0 

0 

0 

2 

0 

17. .. 

20 

980 

90 

6 

0 

0 

0 

6 

0 

18.. . 

22 

740 

80 

4 

0 

4 

0 

1 6 

0 

































28 


Dates. 

Water Used. 

Water Filtered through Carbo-calcis. 

Filter No. 1. 

Filter No. 2. 

' Filter No. 3. 

Sampling. 

Examination. 

Total number of 
bacteria per c.c. 

Liquefying. 

Total number of 

bacteria per c.c. 

Liquefying. | 

Total number of 

bacteria per c.c. 

Liquefying. 

Total number of 

bacteria per c.c. 

Liquefying. 

1900 



1 







Oc. 19... 

Oct. 25 

850 

60 

6 

0 

4 

0 

8 

0 

20. . . 

24 

1,600 

120 

4 

0 

4 

0 

6 

0 

22.. . 

25 

1,360 

80 

6 

0 

6 

0 

4 

0 

23. . . 

26 

1,260 

130 

4 

0 

4 

0 

4 

0 

24. . . 

27 

2.500 

120 

0 

0 

0 

0 

4 

0 

25. . . 

29 

2,200 

120 

2 

0 

8 

0 

0 

0 

26. . . 

31 

1,650 

80 

6 

0 

8 

0 

2 

0 

21 ... 

Nov. 1 

1,250 

90 

4 

0 

6 

0 

4 

0 

29. . . 

2 

1,420 

100 

10 

0 

12 

0 

6 

0 

31. . . 

5 

1,340 

100 

8 

0 

0 

0 

4 

0 

Nov, 1. . . 

5 

1,650 

140 

4 

0 

6 

0 

4 

0 

2. . . 

6 

1,900 

150 

0 

0 

6 

0 

8 

0 

3. . . 

8 

2,150 

180 

4 

0 

0 

0 

4 

0 

5... 

8 

1,720 

130 

0 

0 

6 

0 

2 

0 

6. . . 

9 

3,420 

220 

4 

0 

0 

0 

2 

0 

7. . . 

10 

3,840 

190 

6 

0 

2 

0 

2 

0 

8. . . 

12 

2,000 

160 

1 

0 

8 

0 

2 

0 

9. . . 

13 

2,900 

260 

7 

0 

6 

0 

11 

0 

10. . . 

14 

4,350 

200 

4 

0 

0 

0 

3 

0 

12. . . 

16 

2,700 

160 

8 

0 

7 

0 

0 

0 

13. . . 

17 

1,920 

140 

3 

0 

0 

0 

5 

0 

14. . . 

17 

1,600 

100 

0 

0 

2 

0 

0 

0 

15. . . 

19 

2,090 

160 

8 

0 

6 

0 

4 

0 

16. . . 

20 

2,630 

200 

8 

0 

0 

0 

4 

0 

17. . . 

21 

5,110 

270 

6 

0 

8 

0 

12 

o 

19. . . 

23 

2,700 

210 

4 

0 

10 

0 

7 

o 

20. . . 

24 

3,200 

130 

12 

0 

6 

0 

12 

o 

21. . . 

24 

5,250 

400 

2 

0 

10 

0 

6 

o 

22. . . 

26 

2,640 

230 

6 

0 

4 

0 

2 

o 

23. . . 

27 

18,600 

800 

10 

0 

15 

0 

12 

o 

24. . . 

28 

6,400 

500 

8 

0 

6 

0 

11 

o 

26. . . 

30 

5,000 

230 

7 

0 

11 

0 

5 

o 

27. . . 

Dec. 1 

5,820 

320 

4 

0 

5 

0 

2 

o 

28. . . 

3 

8,150 

400 

3 

0 

9 

0 

1 

o 

30. . . 

4 

13,000 

590 

6 

0 

5 

0 

2 

o 

Dec. i.. . 

5 

11,560 

500 

9 

0 

7 

0 

4 

o 

3.. . 

7 

11,000 

410 

4 

0 

6 

0 

7 

o 

4.. . 

8 

5,640 

160 

3 

0 

2 

0 

6 

o 

5 . . . 

9 

6,950 

200 

3 

0 

4 

0 

1 

o 

7.. . 

11 

9,760 

190 

6 

0 

7 

0 

4 

o 

8.. . 

12 

12,100 

210 

2 

0 

8 

o 

1 

o 

10.. . 

14 

10,620 | 

170 

3 

0 

4 

0 

s 

o 

11.. . 

15 

9,340 

140 

6 

0 

2 

o 

3 

o 

12. . . 

17 

13,200 

220 

7 

0 

0 

o 

9 

o 

13. . . 

18 

16,240 

340 

1 

o 

5 

o 

3 

o 

14. . . 

18 

10,430 

260 

0 

o 

8 

o 

11 

o 

15.. . 

19 

9,210 

160 

6 

0 

8 ;! 

0 

2 

0 


During the first period—from September 8th to October 16th—with 
three exceptions the water applied to the filters was practically pure. 
The number of bacteria found in the filtered water was altogether out 
of proportion to that introduced into the filter with the applied 
water. An interested or insufficiently informed witness would have 




















































































29 


rushed into print at once without waiting for the end and would have 
said that the charcoal was a breeder of microbes, a nest of infection, a 
dangerous thing, etc., while on the contrary it was simply purging 
itself of its own harmless air germs. Any one familiar with the work of 
Professor Tyndal, entitled “ Floating Matter in the Air,” will remem¬ 
ber his explanation of the fact that the desiccated air germs or spores 
require a certain period of incubation in water in order to become adult 
bacteria. This is just what takes place in granular bed filters at the 
beginning of their use. Charcoal, for instance, contains fourteen times 
its volume of air and therefore a corresponding quantity of dry air 
germs. These, under the influence of the moist environment, become 
soft like wheat in a field after the rain; they germinate or grow until 
they are able to move and work their way out. 

On October 11th the filters were rid of all their pre-existing or “ con¬ 
stitutional” bacteria, and the filtered water was as good as the applied 
water. This continued till October 16th, when a change was made. 

Instead of feeding the filters by hand with pure water once during 
the day, allowing them to rest at night, an arrangement was made to 
filter raw water in a continuous manner, day and night, with the result 
that during the three following months the filtrate maintained itself 
practically free from bacteria all the time. 

Surely this is sufficient to show that animal charcoal is not, per se, 
favorable to the growth of micro-organisms. 

The observers who have found fault with charcoal have not carried 
their experiments far enough. They have assumed that charcoal 
could be sterilized by heat as easily as glass, which is not the case. 
They have also ignored the fact that a charcoal “granular bed filter 
is not made to be handled in the same manner as the porcelain porous 
wall” filter! It is made to filter water, not to be put in the fire. A 
process of sterilization which is suitable for a porcelain filter is not 
necessarily good for a charcoal or sand filter. 

The “porous wall” filters are sterile when they are new; they come 
from the fire and contain few, if any, air germs, that is why they give 
sterile water at first. 

The “granular bed” filters, on the contrary, are not free from air 
germs when new; they contain spores and dry germs which at first 
appear to make the water worse; but after a short period of sei\ice, 
these spores or germs have disappeared and the filters become good, 
and remain good as long as they are not disturbed. 

This was confirmed by experiments with sand filters. We took three 


30 


percolators and filled them with sand; the sand in the No. 1 and No. 2 
was not washed, but was subjected to dry heat; the sand in No. 3 was 
washed before being placed in service. The following are the results: 


TEST OF SAND FILTERS. 
Results from October 9 to October 19. 


Date of 
Operation, 

1900. 

Number 
of Bacteria in 
Applied Water. 

Number of Bacteria in Filtered Water. 

Filter No. 1. Filter No. 2 . Filter No. S. 

Oct. 9. 

.28 

20 

10 

800 

10. 

.28 

16 

8 

120 

11. 

.24 

30 

100 

330 

12. 

. 8 

108 

150 

140 

13. 

. 10 

24 

20 

100 

15 . 

. 8 

18 

20 

82 

16. 

. 10 

14 

12 

50 

17 . 

. 8 

12 

15 

56 

18. 

. 8 

4 

6 

12 

19 . 

. 8 

6 

6 

12 


We see that it took four days for the spores in the dry sand to de¬ 
velop into bacteria. Those of the sand which had been washed had 
evidently been incubated and developed into bacteria by the water 
used to wash it. The first filtrate was the worst. It took nine days 
to “ripen” the three filters; that is, to free them from their “consti¬ 
tutional” bacteria. 

At this time it was noticed that the metal screen at the bottom of one 
of the percolators had been displaced. We took the “ripe” sand out 
carefully, removed the metal screens, and made a gravel underdrain 
similar to that used in big filters. We replaced the “ripe” sand care¬ 
fully on this underdrain and proceeded with the filtration. It should 
be stated that the gravel had not been washed or sterilized in any way; 
it was taken out of the warehouse, and was evidently covered with dust 
and dry air germs or spores. It will be observed (page 31) that after 
restarting the filters we have the same curve—the same rise and fall— 
in the number of “constitutional” bacteria as with the charcoal. It 
took twenty-one days to “ripen” the gravel. 

There is nothing new in the discovery that the water coming from an 
unsterilized granular bed filter contains many bacteria, but what is 
new is the fact that if you continue filtering water through granular 
beds long enough, without disturbing the filtering materials, these will 
sterilize themselves without the help of dry heat, steam, or chemicals. 
It is therefore an error to say of granular charcoal or sand filters that 
they must be cleaned or artificially sterilized frequently. 












31 


The following is the record of the performance of these filters after 
the change: 

TEST OF SAND FILTERS (Continued). 

Results from October 10 to November 15. 


Date of 
Operation , 

Number 
of Bacteria in 

Number of Bacteria in Filtered Water. 

‘1900. 

Applied Water. 

Filter No. 1. 

Filter No. %. 

Filler No. 3. 

Oct. 20..., 

.12 

416 

120 

108 

22..., 

. 8 

860 

1120 

1500 

23... 

.8 

2280 

6720 

3460 

24... 

.10 

2820 

7260 

3560 

25... 

.32 

3360 

9000 

2860 

27... 

.10 

1520 

2840 

1060 

28... 

.10 

2460 

6520 

2240 

29... 

. 8 

212 

1360 

190 

31... 

. 8 

200 

1400 

180 

Nov. 1... 

.10 

180 

1280 

160 

2... 

.10 

90 

920 

84 

3... 

.10 

80 

656 

54 

5’.. 

. 8 

68 

592 

58 

6... 

.10 

72 

216 

40 

7... 

. 8 

100 

196 

46 

8... 

. 6 

84 

412 

49 

9... 

. 8 

46 

440 

12 

10... 

. 8 

36 

70 

24 

11... 

. 8 ' 

60 

72 

32 

13... 

. 8 

32 

42 

24 

14... 

. 8 

16 

10 

8 

15... 

. 8 

10 

8 

6 


Domestic and Army Filters. 

We hkve seen that water can be deprived of dangerous bacteria and 
rendered safe for drinking by filtration through improved municipal 
•- slow sand filters as at South Bethlehem and Lancaster. We have also 
seen that failure has sometimes attended the operation of some of the 
large slow sand filters in this country—as for instance at Poughkeepsie, 
Hudson, Little Falls, N. Y., Ashland, Wis., Rock Island, Ill., etc. 
Unsatisfactory sanitary results have also been registered at certain 
times with the mechanical filter plants, Newcastle, Pa., Lexington, 
Ky., etc. At Bangor, North Wales (Great Britain), an epidemic of 
typhoid fever raged for some time and ceased when the use of the 

municipal filters was discontinued. 

The question of domestic filters, therefore, must be of real interest 
to every one of us, not only for those who reside in cities, but also for 
those who live outside city lines. In country residences and on farms 
the water supply is generally drawn from shallow wells, surface springs, 
or cisterns. These supplies are very liable to be bad. 

Armies, likewise, are peculiarly exposed to water-borne diseases, par- 
























32 


ticularly to dysentery. Any government which neglects to provide 
ample means for purifying the water supply of armies in the field is 
little short of criminal. 

The English and French armies in the Crimean War lost'25 per cent, 
of their effective force through diseases due to bad water. The Eng¬ 
lish expedition, organized for the relief of Gordon, in 1884, on the con¬ 
trary, broke all records in health. Twenty-two thousand men returned 
home from Egypt after a march up the Nile and through the desert 
without having lost a single man from bad water. These troops were 
supplied with filters designed by the writer. 

The relation between bad water and disease is so. well established 
that it would be simply foolish to ignore it. 

A simple narration of the successive steps in the writer’s search for 
methods of purifying water for domestic and army use may be of 
interest. 

In 1878 the need of a system of water purification was brought home 
to the writer while residing in London, England, and it was then that 
he determined to consecrate the rest of his life to this particular study. 

It was not until 1882 that he had some sort of a water filter to show. 
In 1884 it was perfected. The invention has since been developed to 
its present state of perfection. 

The first requirement suggested by the English sanitary engineers 
was for a filter that could be cleaned; the second, for one that would 
contain no substance capable of decaying; the third, for a filter that 
would not only clarify the water well but would also remove the or¬ 
ganic matter and metallic poisons in solution. 

Then came a demand for the removal of lime from the water. 

About the same time (1883) the English War Department became 
interested in water filtration and called for designs of: 

1. Pocket filters. 

2. Filters for officers’ “mess.” 

3. Filters for a “squad.” 

4. Filters for a “section” of soldiers. 

5. Filters for a “ company.” 

6. Filters for a “whole regiment.” 

7. Special filters for carrying on pack-saddles, on water-carts, on 
the ambulance and company carts. The forms were to be varied to 
suit the particular kind of transportation desired; some were to be 
made for carrying by hand and others on men’s backs, others again to 
be moved on wheels. 


33 



The public also demanded various forms of filters: 

8. Crockery filters, like coolers, for use in the kitchen. 

9. Decorated porcelain filters for the dining-room. 

10. Stationary filters for attachment to the wall and connection with 
the service pipe in the kitchen or pantry. 

11. Other filters were wanted to filter the water in the garret along- 


jr IG> ip_ The Different Kinds of Water Filters Designed for Army and 

Home Use by the Author in 1884. 

side the house tank, the filtration going on slowly day and night and 
the filtered water accumulating in the tank, from which it was drawn, 
as required, for baths, kitchen, and general use. 

12. The writer found in this country another want, essentially 
American, i. e., a filter that should filter the water as fast as required 
for all usages without storage! A filter that would do in one hour what 
takes twenty-four hours abroad. 

3 
















34 


The very first filter made by the writer (in 1878) was designed to 
clarify wine, brandy, and whiskey. It consisted of a tinned copper 
filter case and a hollow wooden filter frame covered with canvas cloth 
of the kind used in filter presses. A few sheets of filter paper were 
beaten in hot water, the water was squeezed out, and the pulp beaten 
again in some of the first fluid (brandy or whiskey) which was to be 
filtered. This first fluid or emulsion would carry the floating pulp 
onto the surface of the cloth, where it would become deposited evenly 
and make a new filtering membrane having the appearance and con¬ 
sistency of a thick sheet of blotting paper. The first fluid was, of 
course, refiltered. It was passed over and over again, several times 
through the filter, until it came out perfectly bright. Many of these 
filters are still in use in old and New England. 

The first Maignen water filter was made in 1879. Woolen felt was 
substituted for canvas, and finely powdered charcoal took the place of 
the paper pulp. The reason for this addition of a filtering membrane 
was the conclusion that no textile, however carefully made, could 
have pores absolutely uniform in size. There appeared only one way 
to insure a homogeneous surface, and that was to float in the first liquid 
very fine particles of suspended matter which would at first flow in 
greatest quantity toward the largest passage and in less quantity toward 
the smallest pores, until after a time the whole surface would offer the 
same resistance. 

Felt was selected for water filtration because it was known to have 
been used from time immemorial in the arts for filtering purposes. The 
felt bag was the filter of the alchemists and it was sometimes called 
“Hypocrates’ sleeve.” It is felt which has given the name “ filter” to 
the device intended to separate solids from liquids. 

This first water filter with felt and charcoal gave good results for 
about a week. Then the filtered water began to have a faint odor; 
at the end of another week it smelt like bad eggs, and in three weeks 
the microbes had made short work of the wool—it was rotten. There 
never was a second felt filter made for water. 

In 1880 the writer found that the art of spinning the mineral fiber 
known as asbestos had been recovered after having been lost for many 
centuries (the ancients had used asbestos cloth for cremation, very much 
as we do now), but it was necessary to mix cotton with the asbestos 
fiber as a binder. The cotton soon decomposed in water and gave a bad 
taste to the water. Later it was found possible to dispense with the 
cotton, but on the condition of using oil. This was nearly as bad and 


35 


gave a very objectionable taste to the filtered water. So, in order to 
get rid of these objectionable features, the asbestos cloth was baked in 
a furnace at such dry heat as would burn a straw. It was more than 
ten years before mechanics devised machinery capable of spinning and 
weaving pure asbestos fiber. 

Many other difficulties were of course encountered. The greatest 
was that of spinning the asbestos thread loose enough to have filtering 
qualities and yet strong enough to stand the strain of weaving. This 
was ultimately overcome. 

It was not enough to have a good filtering cloth. It had to be used 
to advantage. In the first filters made, the cloth was sewed in the 
shape of a cone and tied over a perforated hollow cone for the small 
domestic filters, and over tinned copper hollow filter frames for the 
larger filters. Then the powdered charcoal was deposited on the cloth, 
as already explained, by being mixed with the first water put into the 
filter. If the tying of the cloth on the cone, or the sewing was defective, 
the charcoal would come through with the filtered water and thus indi¬ 
cate the defect. It was not long before it was found that the tinned 
copper frames underwent “electrolysis.” The metals were half dis¬ 
solved by the pure water in less than one year. 

At that time two suggestions presented themselves—(1) to do away 
with the metal as a support for the asbestos cloth, and (2) to multiply 
the filtering surface, so as to get more water. The evolution from the 
cone to the concertina shape of the present filter frames then followed. 
Let us fancy that we have before us a cone; let us squash it like an 
opera hat; we shall then have a large surface of cloth in a compara¬ 
tively small space. Or let us take a plain sack or cloth cylinder such as 
is used to hold wheat; let us tie one end, then insert inside the sack a 
ring of the full diameter of the sack to distend it. Then let us pass a 
small ring outside the sack to constrict it; then another large ring in¬ 
side, and another small ring outside, and so on, six or eight times, and 
we have then the notion of the concertina shape. We have more than 
24 sq. ft. of area in a space one foot square, eight inches high. 

But we then met with trouble; the inside rings did not prevent the 
two folds of the cloth from coming together and adhering to one an¬ 
other under the force of suction inside or compression of the water 
outside. 

These changes, which are described in a few words, did not succeed 
one another in so short a time. Weeks, months, and years intervened 
between the different steps, and the new ideas came when they were 


36 


least looked for. It was the sight of a wire-netting screen in a custom¬ 
house office in Milan, Italy, that gave the idea for the next step. It 
was made of spiral wire. A number of discs were made and used in a 
lecture at Rome within a few days of the first thought. They worked 
admirably; the space between the two edges of the spirals prevented 
the two cloths touching one another and made a good draining system. 
The first discs were nickeled and some silver-plated, but it was still 
metal and we knew that it would not stand long. 

The writer was then back in London. He took his spiral wire frame 
to a pattern-maker, explained to him that he wanted a corrugated and 
perforated disc in pottery to have the same properties as the wire disc, 
and in less time than it took to explain what was wanted the pattern¬ 
maker had settled the problem. 

He took a piece of wood about one inch thick and six inches square 
and cut parallel triangular grooves in each face deeper than half the 
thickness of the block, those in one face at right angles to the ones in „ 
the other face, so that at each intersection of a groove with those on the 
opposite side a hole was made, giving a corrugated and perforated 
block that would secure in a filter practically the same effect as the 
spiral wire cloth. 

This pattern was taken to the pottery and served as a model for 
moulds with which the porcelain discs now used are made. 

To have found a filtering cloth not subject to decomposition in water, 
and to have arranged it so as to provide the maximum area of filtering 
surface within a given space, was not enough to constitute a water 
filter answering all the requirements, although asbestos cloth alone, 
when well felted, is able to clarify water to perfection—better than 
“granular beds” and “porous walls.” It has been found capable of 
sterilizing wine without changing the taste, color, or any dissolved 
property. It can, therefore, clarify water, but it cannot purify it. 

It. was then decided to deposit on the surface of the asbestos cloth 
some finely powdered charcoal, the particles of which were to be of 
such size as not to rise to the surface of the water nor sink to the bot¬ 
tom. It must permeate the whole body of the water and remain in sus¬ 
pension for some time. The filtration is then started, and as the water 
passes through the asbestos cloth the current draws the small particles 
of charcoal toward the surface of the cloth. 

If there be in the asbestos cloth some pores or channels larger than 
others, the water flows in the direction of the largest openings with the 
greatest velocity. It therefore carries in that direction the greatest 


37 


number of fine particles of charcoal and this goes on automatically all 
over the asbestos cloth. It is easj' to understand that in this manner 
the filtering surface is equalized and rendered perfectly homogeneous. 

It should be stated that the filtration through asbestos cloth does 
not take place as through a sieve or as through a “granular bed” or a 
“ porous wall. ” The water ascends or descends along the asbestos fila¬ 
ments as oil along a lamp wick. This is evidenced by the fact that 



jr IG 12 _Appearance of the Inner Fig. 13. —Appearance of a Maignen 

Asbestos Cloth or Core A in Filtering Organ in Water. Ob- 

Water, before it is Coated with serve the Hairy Appearance of 

the Finely Powdered “ Carbo- the Asbestos Felted Cloth. 

Calcis.” The Filtration Takes These Loose Fibers Fill the 

Place by Capillarity, and not Meshes of the Cloth and Pre- 

by Straining as in Other Filters. vent the Mud Penetrating. 


when a filtering organ, such as has been described, is placed in a vessel 
containing water and is used as a syphon, every drop of water which 
is in the vessel is sucked up and filtered out. 

With any other material the syphon would be broken off as soon as 
any part of the organ would be above water. The air would penetrate 
through the pores of porcelain or any other kind of porous or granular 
filter. The air does not go through wet asbestos cloth. 




38 


The invention was at this stage—asbestos cloth stretched on frames 
and covered with powdered charcoal—when the British army was 
equipped with filters designed by the writer for the Egyptian cam¬ 
paign. The instructions were to wash off and renew the fine charcoal 
once a week. The filters could thus give a very large quantity of water 
of high quality, as has been proved by the results already alluded to. 



Washing the Mud off the Surface of the Filtering Organ. 



Fig. 14. 

A is a special asbestos cloth arranged in concertina shape by means of porcelain 
discs P P which distend the sack and asbestos cords which constrict it. 
B is a thin layer of finely powdered “ Carbo-Calcis.” C is a thick layer 
of granular “ Carbo-Calcis.” D is an outer asbestos cloth or sack. 

The next step in the progress of the invention was that which con¬ 
sisted in surrounding the powdered charcoal with a thick layer of 
granular charcoal. This had the result of lengthening the life of the 
powdered charcoal, as most of the mud was retained by the coarsest 
layer, and, instead of having to be cleansed once a week, the filters in 
which the granular charcoal was placed could go a month or more 
without washing. 
























39 


Another step, and this was the last, consisted in covering the granular 
charcoal with another asbestos cloth. This would keep away the mud 
from both the granular and the powdered charcoal, so that these porous 
materials can keep their porosity and power of oxidation for an in¬ 
definite length of time. 

Thus constructed, the filter was found capable of removing from 
water not only the bacteria and the suspended matter, but also the dis- 



Fig. 15.—U. S. Army “Section” Filter (Maignen System). 

Tacked for transport in two telescoping buckets with cradle to protect the 
filtering organ against injury during transportation or use. 

solved organic matter, such as urine, and the dissolved metallic poisons, 
such as lead, copper, and iron. 

This power was not due to the asbestos, nor to the granular charcoal, 
nor to the powdered charcoal alone, but to the combination of the 

whole. ... 

In the schools of hygiene in Europe this filter is used to illustrate 

the power of filtration. Thus Dr. Arnould, of Lille, France, m his 






















































40 


book, “Nouveaux Elements d’Hygiene,” says: “An elegant experi¬ 
ment consists in adding to a glass of water a few drops of urine. You 
show the students that this polluted water discolors instantly a weak 
solution of permanganate of potash put, drop by drop, in the water, 
you then filter the water through a Maignen filter, and doing the same 
as before with permanganate, you show that the pink color of the re¬ 
agent is not in any way altered.” 

Professor John Marshall, of the University of Pennsylvania, and Dr. 


Fig. 16.—Filtering from Dish to 
Bucket. 



Fig. 17.—“Cottage” Filter. Form 
Best Known in England and 
Europe for Family Use. 


C. H. White, of the U. S. Naval Museum of Hygiene, Washington, 

D. C., have found it capable of removing dissolved arsenic. 

Some have called this the power of “oxidation,” others “molecular 
attraction,” others “contact” (as in the case of spongy platinum); 
others again, the “power of the powders.” 

Whatever the explanation the fact remains that this filter removes 
dissolved organic matter and dissolved metals. It does not remove 
sodium chlorid, nor sugar, nor the salts of the metals of the first series: 
lithium, sodium, potassium; it removes a small quantity of the salts 


































41 


of the metals of the second series: calcium and magnesium: and the 
entirety of the salts of the heavy metals: lead, iron, copper, mercury, 
etc.—dissolved in water. 

Porcelain filters are used for separating bacteria from their toxins. 
The filtered fluid is as toxic after filtration as before filtration. If 
such a fluid be passed through the Maignen filter it is deprived of both 



Fig. is.—“S ervice” Filter. 


Fig. i9 _—Asbestos and Charcoal 
Pressure Filter as Used in the 
Schools of Philadelphia. 


the bacteria and the soluble toxins. The following are a few of the 
experiments which have been made in order to ascertain this fact: 


By Dr. Mac6, Nancy: 

“A virulent anthrax broth was prepared; five drops sufficed to kill 
i guinea-pig. This broth is put directly into the filter; water is after- 
vard put in the filter. The water which has traversed the polluted 
















42 


filter is collected and is injected at the dose of two c.c. to two guinea- 
pigs. These are not affected in any way. This operation is repeated 
several times during one month with the same filter without steriliza¬ 
tion or cleaning, and with the same result. The guinea-pigs inoculated 
with the polluted water before filtration died. Those inoculated with 
the filtered water did not suffer.” 

By Dr. Burlureaux, Paris: 

“Water charged with anthrax germs kill inoculated mice. The 
same water after filtration has no effect on them.” 

By Dr. M. Gillespie, in the Maignen Laboratory, Philadelphia: 

“A bouillon culture of diphtheritic bacteria was prepared by inocu¬ 
lating ordinary sterilized bouillon with a pure culture of diphtheria 
bacillus. It was placed in the incubator for development and kept at 
37.5° C. for one week. At the end of that time, it was of such viru¬ 
lence that half a cubic centimeter per hundred grammes of weight of 
guinea-pig would be sufficient to kill the animal. This bouillon culture 
was filtered through eight layers of filter paper to free it of the bac¬ 
teria. To the resulting pure toxin one-half of 1 per cent, of tricresol 
was added as a preservative. One and seven-tenth cubic centi¬ 
meters of this toxin was inoculated into a guinea-pig of 270 grammes 
weight. The animal died in forty-eight hours. 

“About 300 c.c. of this toxin were then filtered through a Maignen 
filter; the filtrate was as clear as water; the yellow color of the bouillon 
had been removed. One-half of 1 per cent, of tricresol was added, 
as had been done in the case of the unfiltered toxin. A guinea-pig 
of 274 grammes was inoculated with 1.7 c.c. of the filtrate, and it 
showed no symptoms of suffering, and is now enjoying perfect health.” 

The filter also removes gases and bad taste. This quality is notice¬ 
able with the Philadelphia water which at certain times of # the year 
has a very unpleasant taste and odor due to sewage and organic pollu¬ 
tion. The odor is particularly strong when the water is heated or 
boiled. After filtration by this process the water is free from bad odor 
or bad taste. 

Figs. 16, 17, 18, and 19 show different ways of using the Maignen 
asbestos and charcoal filtering organs. 

The following is the record of some of the school filters (Maignen 
system) after five years’ constant use, during which time it was not 
cleaned more than four times. 

Bacteria per c.c. 


Raw water applied to the filter of the “U. S. Grant ” School, 

Seventeenth and Pine, Philadelphia,. 2800 

Filtered water . i g 

Efficiency, 99.38 per cent. 

Raw water applied to the filter of the “Hollingsworth ” School, 

Locust above Broad, Philadelphia,. 2900 

Filtered water . 22 

Efficiency, 99.21 per cent. 






No 9 




43 



Fig. 20.—Double Pressure Filter (Maignen System). 












































































































44 


Little need be said about that class of filters which are installed in 
cellars and are supposed to filter the water as fast as if there were no 
filter at all. The writer has made some of this kind with coke and 
sponge in a cylinder as a scrubber, and granular charcoal in another 
cylinder, as a final filter. They should be kept going without cleaning 
or disturbance as long as they give enough water, and when they cease 
to do so all the materials should be taken out, thoroughly washed, and 
replaced carefully in the cylinders. Partial cleaning is not advisable 
and daily washing by reverse current much less so, because, as we have 
already seen, granular bed filters are never as. good after being dis¬ 
turbed as when left alone. “Make room for the mud” and “disturb 
the filter as little as possible” are the thoughts which have been fore¬ 
most in the mind of the writer for some time past. 

Most engineers and inventors of filters have hitherto made the mis¬ 
take of asking too much from a single operation or process. The 
writer was at one time under the same narrow influence, but he was 
years ago brought to his senses while attempting to filter large quanti¬ 
ties of wine with asbestos cloth in the south of France and in Algeria. 
He had a very fine asbestos filtering cloth and expected great results 
from it. If the wine came out bright the quantity filtered was insignif¬ 
icant, and if the flow was forced by pressure or suction in an attempt 
to get a larger quantity the filtered wine was not clear. In this dilemma 
he decided to filter twice in succession, first through an open asbestos 
cloth, which would remove 60 or 80 per cent, of .the organized cells 
(which made the wine cloudy), and next through a closely woven 
asbestos cloth, which would finish the clarification. The result was a 
revelation. The two operations gave, in the end, both quality and 
quantity. 

From that time onward preliminary filtration was established in 
the mind of the writer, and it is safe to predict that in the future a 
multiplication of filtering operations jvill prevail over single opera¬ 
tions. Subdivide and distribute the labor according to the capacity 
of each laborer. Do not put the work of a porter on the shoulders of a 
gentleman, and do not put the work of a gentleman in the hands of a 
porter. 

In dealing with the purification of large water supplies' it is well to 
consider the different subdivisions of the work as now understood: 

1. The idea of sedimentation in reservoirs is to retain the particles 
of coarse silt and sand which are heavy enough to fall by their own 
weight to the bottom; also as a reserve to draw from in case of acci- 


45 


dent or during freshets, and also in order to render the transition from 
the good to the bad water less marked owing to the admixture of the 
two waters in the reservoir. 

2. The idea of scrubbing is to retain the greater part of the bulky 
and light suspended matter, such as algae, leaves, clay, etc., which 
clog the filter prematurely. Scrubbers designed for this purpose 
should lose the least possible amount of head. 

3. The idea of 'prefiltration is to help the final filters by doing some 



F IG . 21. —Home Water-softening Apparatus (Maignen System). 

of their work and thereby lengthening the “runs” and diminishing 
the risk of bad work. 

4. The idea of filtration proper or final filtration is to retain the bac¬ 
teria left in the water after the preliminary treatments. 

. Many other subjects relative to water purification, such as coagula¬ 
tion, influence of the air on filters, positive and negative head, loss of 
head, rates of filtration, etc., might be discussed, but would extend 
the limits of this paper unduly. The question of the removal of lime 
from water has, however, already been raised in this paper. 

Lime cannot be removed by filtration. The writer invented in 1884 a 
water-softening process, which has continued in vogue in England to 
this day, for country residences and public institutions in districts 
where the water is hard. 










46 


In this process the reagents—mostly lime and soda are prepared 
in a powdered state, in the proportions indicated by the analysis of 
the hard water. The softening powder is kept dry in iron barrels or 
tins. 

An automatic apparatus with softening tank is installed at the top 
of the house. As the water comes into the tank it passes over an 
overshot water-wheel which provides the power necessary to drive 
the powder out of the hopper through a regulated door. The hopper 
is filled once a week or so by the gardener or house-servant. The 
powder and the water come together in the desired proportions into the 
tank. It is filtered after the chemical reactions are ended and no 
trouble has ever been experienced, though more than four hundred 
installations have been in use in England during the last fifteen or 
twenty years. 

These installations deal with the whole water supply of houses, 



Fig. 22. —Water Pipes Incrusted with Lime Deposit from Hard Water. 

not only to prevent incrustations in hot water pipes but also to supply 
soft water for drinking, cooking, baths, etc. 

The powdered preparation alluded to is known as “ anti-calcaire,” 
and can be obtained and used without apparatus. It can be added 
to water in any kind of tank, tub, or vessel. The powder is mixed 
with the water in the evening, and the next morning the water is soft 
and clear and the lime is at the bottom of the vessel as a heavy sedi- ♦ 
ment. 

Dr. Burlureaux, of Paris, and the writer established fifteen years 
ago that the chemical purification of water, which is effected by this 
softening process, brings about as a natural consequence its steriliza¬ 
tion. 

The tests of Dr. Burlureaux, which lasted more than two years, and 
in which quite a number of the most noted Paris bacteriologists par- 









47 


ticipated, were made with various kinds of bacteria: cholera, typhoid, 
coli, streptococci, and anthrax. 

The following is the record of one of these experiments, made with 
anthrax bacillus, and which may be taken as a type of the technique 
followed: 

“To one-half liter of hard well water was added a culture of anthrax. 
Ten drops were planted on a gelatin dish as control. One-half gramme 
of ‘ anti-calcaire’ was added to the sample of polluted water making 
the dose 1: 1000. Samples of ten drops were taken at different hours 
and planted on gelatin, with the following results: 


Samples Planted, Dec. 22. 
Date of Read-_ 


ING OF THE 

Cultures. 

At 7 A. M. 
Control. 

At 10 A. M. 
Treated Water. 

At 3 P. M. 
Treated Water. 

At 6 p. M. 
Treated Water. 

Dec. 24, at 3 
P. M. 

The plate was 
covered with 
colonies of B. 
anthrax and 
B. fluorescens 
viridis. 

About half the 
number of col¬ 
onies as com¬ 
pared with the 
control plate. 

No colonies ap¬ 
parent. 

Nothing. 


DISCUSSION. 

Henry, Leffmann. —The problem of water supply is an acute one, and in 
view of the constantly accelerating rush into cities, the problem will become 
more and more serious. In most parts of the world, ordinary wells or springs 
will not suffice for cities, and they must draw their water from rivers and other 
large sources, which are sure to be polluted, and the problem is to prepare them 
for domestic use. 

The question raised by this paper in regard to the previous treatment of the 
water is a bone of contention among scientists and sanitarians, and I feel that 
we cannot yet afford to unreservedly admit it as a fundamental method of 
purification. I believe the ideal methods will be those which are able to secure 
the purification of the water without the introduction of chemicals. They 
change the constitution of the water; they affect it for manufacturing as well 
as for domestic purposes, and they always, I think, put the medical profession 
of a community more or less in antagonism to the public authorities. On this 
basis I have always felt unwilling to promote the purification systems that 
provide for the use of chemicals. In private supplies, for instance, that of 
Girard College, where the medical control is under the complete control of the 
organization of the college, it is possible to establish a filter system, as has been 
done there, with the use of a coagulant, and to conduct it satisfactorily. The 
supply is not very large, and the management can regulate the operation as 
it pleases. Under such circumstances, a system of filtration has been installed 

















48 


which has had a remarkable effect on purifying the water. Girard College is 
located in a district where the water is bad, as bad as in any part of Philadelphia, 
and I know that when in some laboratories in that district I draw the water 
for experiment, it is “distinctly visible” at a distance. Right in the midst of 
this district in w r hich typhoid is prevalent, Girard College has escaped. In 
some views I showed here some time ago, dealing with the subject of typhoid, 
Girard College was shown in a plan of this district as being situated very much 
like an island, that is, with regard to typhoid statistics. Of the efficiency of 
the system there can be no question. It is a remover of microbes, and it is a 
means by which filtration can be made much more rapid. The results obtained 
at Lancaster and at other plants are those which would be expected from such 
a system, but the question in my mind is, whether we cannot do without the use 
of chemicals in filtration. These systems may be justifiable; I do riot say they 
are necessarily dangerous, but I think they are, in a measure, not along the best 
line of development. 

The author of the paper has challenged this view to a certain extent, and 
perhaps justly so. Nature may not always be operating to the best interests 
of the human being. The human being is only one of the many organisms 
that the world contains, and her processes are sometimes remarkably antago¬ 
nistic, but this precipitating method has a degree of unnaturalness that perhaps, 
we ought to avoid. If we use chemicals they disturb the condition of the water, 
including its use as a manufacturing material. Manufacturers at Manayunk 
some years ago gave up the use of alum, which greatly increased the hardness 
of the scale in the boilers, by'substituting a sulfate for a carbonate. 

It has seemed to me, in looking over these processes, that if we want to intro¬ 
duce chemical methods it might be better to introduce them by chemical treat¬ 
ment of the water after the filtration, allowing the filtration to be rapid and 
capable in itself of removing all microbes. The chief danger from w T ater is 
bacteria. This is a view widely exploited, so that we may safely take it as a 
point of argument. We can kill microbes by various methods. One of these 
methods is heat. If we could sterilize water by the direct action of heat on the 
water, we could kill the microbes. In order to furnish water to communities 
that shall be satisfactory, it must be practically clear and colorless. People 
will complain of water that is not clear and colorless, and processes that permit 
of the application of heat do not accomplish this change; they simply sterilize. 
It would be a possible and not at all a fantastic idea, by means of a heat exchange 
system, to practically kill the microbes by a heat filtration process which would 
remove most of the suspended matter and most of the color. 

Another method, and one which was brought before this Club in a rather 
unwise way, is the “ozone” method. It has an advantage over the plans sug¬ 
gested in the paper in the fact that it does not introduce any chemical into the 
water in preliminary treatment. Ozone has a destructive action on most forms 
of mineral life, and the proper ozonization of water will render it practically 
sterile. The ozone, w'hich is a modified form of oxygen, returning ultimately 
to the condition of oxygen, and it cannot result in any permanent changed 
condition. 

We have heard about the copper-sulfate method, which is more or less 
objectionable, and it has been shown to be not by any means certain to kill 


49 


microbes of typhoid, as at first alleged. I still believe, however, that if we 
can get back to our established filtration systems based on that by which nature 
filters, we are on safe ground. Processes <jf filtration of water in nature are 
practically filtration through soil. It is generally accepted that we cannot 
depend upon purification by the flow of water in streams; there is no definite 
point at which a river will purify itself. Filtration through soil is an approved 
and natural process, and if we embody that principle in our filter-beds, we will, 
under proper conditions, accomplish a great deal. 

The disposition of municipalities is to use too small an area for their filtration 
plants, and this probably accounts for the conditions in West Philadelphia. 
They have been trying to filter too fast, and the efficiency of the filters, as given 
to me a few weeks ago, in gallons, seemed rather high. The fact that they had 
cleaned one of the sand-beds a few days before and started to filter within twelve 
hours after the cleaning may be responsible for the condition. The figures, 
as published in the newspapers, of the amount of bacteria also seem rather high 
320, 420, and so on—especially at this time of the year, when the number of 
bacteria is comparatively low. 

We have a little too much dread of the microbes, and perhaps a little too 
much sensitiveness to what is called “the efficiency of filters.” Personally, 

I believe, in regard to household filters, that if they will deliver a clear water, 
they will deliver a safe water. I have for many years had in my house a house¬ 
hold filter which has delivered constantly, with reasonable care, a clear water, 
and I have never had the slightest reason to suppose that it has produced any 
infection. Persons other than myself, who have come from other parts, have 
used the water and never been in any way affected by it. I live in a district 
which has not been served with filtered water, but there is a comparatively low 
rate of typhoid fever, and most of the residents have filters of the proper class. 
The dangerous microbes get taken out by these filters, and it w r ould be a very 
good thing if housekeepers generally were provided with filters of this class. 

I have felt a little sorry that Philadelphia filtration matters have not moved 
a little faster. The proceedings generally have produced a lack of faith on the 
part of the public, and the recent agitation in the newspapers has, I think, 
added to this state of affairs. 

John C. Trautwine, Jr. —Even to those who make a specialty of water 
supply, the purification of water is but one of many subjects claiming attention; 
but our author, with appalling exclusiveness, has devoted more than a quarter 
century to the study of this single branch. When such an authority favors 
us with his views respecting his specialty, our discussion should manifest a 
becoming modesty. 

Nearly ten years ago, while the writer was Chief of the Bureau of Water 
of this city, the question of filtration had long been before the public, and 
was then under particularly active discussion. 

About that time a member of the City Councils, who had been traveling in 
Europe and had seen our author’s asbestos bag filters in use for the purification 
of small municipal supplies in France, described them to the writer and sug¬ 
gested the practicability of their employment for the purification of the water 
supply* of Philadelphia. 

The writer having already had sad experience of the vastness of the volumes 
4 


50 


of water which the good people of Philadelphia insist upon passing into the 
sewers unused, could not help questioning the practicability of filtering these 
enormous quantities through small globular units, each about one foot in di¬ 
ameter, and he feels some satisfaction in the reflection that during our author’s 
study and canvass of the matter as applied to the Philadelphia supply, the 
question of filtering through such small units has not been given extensive, 
if any, consideration. 

A year or so later than the time mentioned, our author came to Philadelphia 
and fitted up a quite elaborate experimental plant at 1310 Arch Street, and 
the writer made frequent and interesting visits to this plant. He had also visited 
the preliminary filters designed by our author, and erected at Lower Rox- 
borough and at Bethlehem. 

The question of preliminary filtration first came to the writer’s notice some 
ten years ago, in a pamphlet describing the system in use at Scheydam, in Hol¬ 
land. 

The advantages and disadvantages (if any) of preliminary filtration seem 
to be somewhat analogous to those of compound and multiple expansion in 
connection with steam-engines. The earlier steam-engines effected all of the 
expansion in one cylinder, but modern developments have increased the number 
of cylinders to two or three or more, and it would seem but rational that the 
work of filtration should be divided between sedimentation, scrubbing, pre¬ 
liminary filtration, and final filtration, as suggested by our author, if indeed 
still further refinement is not eventually found economical, and therefore desir¬ 
able. 

Our author’s comparison of the conditions obtaining at Lower and at Upper 
Roxborough is manifestly favorable to his argument in behalf of preliminary 
filtration, and it is to be regretted that we have not fuller information respecting 
the cost of the improvement evidently obtained through preliminary filtration. 

Our author advises us as to the cost of scraping, transferring, washing, and 
restoring the sand, and as to “other expenses charged (not itemized),” but the 
sum of these he calls “total cost of maintenance and operation,” leaving us 
under the impression that these figures do not include interest and depreciation 
on the preliminary filters. 

With such information before us, it would have been practicable to deter¬ 
mine whether the game was worth the candle; in other words, how nearly the 
same results might have been obtained at the same total cost by increasing the 
area of the slow sand filters. 

Our author’s substitution of well lighted rooms for what he calls the “cata¬ 
combs” of the typical slow filtration plant, must appeal to the layman as a 
distinct advantage, and it would be interesting to learn from experience what 
compensating disadvantages, if any, are to be urged against the innovation. 

The same observation applies to our author’s use of a platform carried by a 
traveler running upon the side walls of the filter for the purpose of cleaning the 
bed, when such cleaning is required. It applies also to the glass tube commu¬ 
nicating with the filtered water under the filter, and thus showing constantly 
the character of the effluent. Our author’s method of washing the sand must 
also appeal to the layman as an improvement upon the usual methods, and the 
writer would be interested to hear what might be said to the contrary. 


51 


Our author informs us that, at Lancaster, “it was considered desirable not 
to change the chemical character of the water,” and that therefore the reagents 
used “simply coagulate the fine suspended matter without making the water 
harder or softer.” The location of Lancaster—in a limestone valley—would 
lead us to expect hard water in the Conestoga River, and, Lancaster being an 
important manufacturing town with many steam-boilers, soft water would 
seem to be a desideratum. The writer would therefore ask why the reagents 
used first, with a view to softening the water, were abandoned, and other reagents 
adopted which left the water “never more acid nor more alkaline after treat¬ 
ment than before”? 

Most of us have been taught to believe implicitly in what our author calls “the 
biological idea,” which teaches us that the “Schmutzdecke,” which forms upon 
a filter-bed, is a battle-field in which the bacteria mutually destroy each other, and 
in which organic matter is oxidized, or “nitrified,” as the experts (for some reason) 
call the process. It was with a feeling akin to shock that the writer learned, some 
years ago, that no less an authority than Mr. Hiram A. Mills, of Lawrence, Massa¬ 
chusetts, ventured to dissent from this doctrine. And now our author has the 
hardihood to refer to it as “pure romance.” 

Even laymen, however, nowadays require something more than an ipse dixit 
from their high priests, and the writer would have been glad to learn the reasons 
for our author’s heresy respecting this generally accepted “biological idea.” 
It no longer satisfies the inquiring mind of the layman to be asked to smile at the 
author’s picture of the “cannibal-like bacteria whose propensity is to eat their 
weaker brethren,” or to be told that “this is pure romance.” If nature had been 
so constituted that her creatures could exist without destroying their weaker 
brethren, this reductio ad absurdum might have had some force. 

Our author tells us that in the environment in which the bacteria find them¬ 
selves when they are caught upon the filter-bed it is impossible for them to devour 
each other, and they have merely to lie still and die. But further on he tells us 
.how microbes similarly caught upon the felt which formed his first water filter, 
made in 1879, “made short work of the wool” and discouraged him from further 
essays in that direction. Surely, if the imprisoned microbes can make short work 
of wool, it is hardly absurd to suppose that they may devour each other, as we 
human beings devour our fellow-creatures even though we may happen to be 
living under unsanitary conditions. 

The writer submits also that our author is disingenuous in his argument against 
the “biological idea,” that “algae do not grow in covered filters,” and that “if 
their presence was necessary to good filtration, their absence in covered filters 
would lead to bad results, which is not the case.” If the writer understands the 
“biological idea,” it contemplates, not an “algean jelly,” but one in which 
bacteria are the active factors, and these, the writer understands, can operate as 
well in the dark as in the light. Our author therefore appears willing to make the 
biological idea ridiculous by showing the absurdity of a claim which the up¬ 
holders of that idea do not make. 

The writer, during his early acquaintance with the author and with his ex¬ 
periments in Arch Street, was much interested in the author’s use of asbestos pulp 
which he mixed with the water in order that it might be deposited as a Schmutz¬ 
decke or blanket upon the surface of the filter-bed. This appeared to have the 


52 


double advantage (1) of hastening the formation of the Schmutzdecke, and (2) 
of facilitating the cleaning of the bed; for the asbestos pulp thus deposited 
cohered sufficiently to permit its removal very much as a sheet of wet blotting- 
paper would be removed. It was therefore a disappointment to the writer 
to be told by experts that the asbestos film thus deposited was open to the ob¬ 
jection that air-bubbles formed under it. 

The writer is therefore interested to learn that our author has substituted 
“fine charcoal and fine coke” for the asbestos of his earlier practice, but in the 
absence of information to the contrary takes it for granted that the particles 
of charcoal and of coke fail to unite in a continuous film, easy of removal, as 
the asbestos particles did. 

In the early days, while filtration was under discussion in England, one of 
its objectors remarked that it was ridiculous to suppose that such treatment 
could do more than merely clarify the water, inasmuch as the microbes present 
in the water “could march a thousand abreast through the interstices left between 
the grains of sand.” 

Our author now gives us to understand that the real function of the Schmutz¬ 
decke, whether naturally deposited from the water or hastened by the use 
of coagulants or artificially produced, as by means of his asbestos or charcoal 
or coke, is not to provide a battle-ground where the bacteria destroy each other, 
but merely to form a trap in which these creatures are caught and permitted 
to die like flies upon “Tanglefoot.” 

The writer has always believed that in placing asphalt over the original 
clay and concrete linings of the Queen Lane and Roxborough reservoirs we 
were merely spreading a fine sieve over a coarser one, thus facilitating the cap¬ 
ture and utilization of the fine particles carried in suspension in the water, 
which particles, thus caught, served to choke the passage and to prevent the 
further escape of water from the reservoirs, and our author’s claim is that the 
Schmutzdecke in a filter-bed acts in a similar way upon the bacteria and in that 
way only. 

Our author criticizes the statement that sand filtration is a natural process, 
or even an imitation of nature, and in support of his criticism points out certain 
differences between nature’s method and that adopted by man. But when 
it is said that sand filtration is an imitation of nature it is hardly intended to 
assert that the imitation is perfect in all respects. On the contrary, filtrationists 
are apt to assert that artificial filtration is an improvement upon natural filtra¬ 
tion—that man, in applying nature’s methods, avoids the mistakes and limita¬ 
tions to which nature is necessarily subject. Our author says: “Nature’s 
sand is not confined between walls. It has thousand of acres to do its work.” 
Surely man has improved upon nature by getting a vastly higher efficiency out 
of his acres. 

In discussing the rapid or so-called mechanical filter our author remarks 
that while a “mechanical” plant is relatively cheap in first cost, its cost of 
operation and maintenance is much greater than that of slow sand filters. It 
would be interesting to know how the two types compare in cost, su mm ing up, 
in each case, the cost of construction and the capitalized cost of operation and 
maintenance. 

Messrs. Rudolph Hering, Samuel M. Gray, and Joseph M. Wilson, the experts 


53 


called in to advise respecting our water supply in 1899, give, in their estimates, 
figures for the cost of operation, maintenance, interest, and depreciation, for 
rapid and for slow filtration, showing only about 4$ per cent, difference in favor 
of slow filtration, on projects for furnishing 450 million gallons per day. 

Annual Cost 
of Operation, 
Maintenance, 
Interest, and 
Depreciation. 


Rapid, filtration: 

From the Delaware at Torresdale. 83,108,606 

Slow filtration: 

150 million gallons per day from the Schuylkill, 

300 million gallons per day from the Delaware near the city.. 2,971,801 


Difference in favor of slow filtration. $136,805 


Among the many objections urged by our author against the “mechanical” 
system, he mentions “the increased amount of incrustating constituents in 
the water.” The writer has been under the impression that where the raw water 
contains lime in sufficient quantities to effect the decomposition of the alum 
or alumina sulphate, the amount of incrustating constituents in the water is not 
increased. 

Our author mentions the fact that certain metals dissolved in water are 
removed by filtration, while other metals, similarly dissolved, are not removed. 
The question of removal, by filtration, of dissolved impurities, has been so often 
brought to the writer’s attention, that he ventures to suggest that this partic¬ 
ular question might properly be made the subject of a short paper by the author. 
In stating that, with proper precautions, it is safe to expose filtered water to 
storage without protection by means of a roof, our author attacks another 
time-honored belief of filtrationists, and it is to be hoped that his statement will 
lead to further discussion of the question, and to the letting in of more light 
upon it. 

His curious and interesting experience respecting the growth of algae in the 
light and their discouragement by darkness, reminds the writer of the experience 
related by a Western engineer respecting a reservoir in that part of the country. 
His reservoir was covered with boards laid with narrow spaces between them, 
the boards and the spaces running from east to west so that the bands of day¬ 
light, sent into the water through the spaces, remained nearly constant in posi¬ 
tion throughout the day. Under these conditions there was considerable vege¬ 
table growth, but when the boards were replaced in a position running north 
and south, so that the bands of light, entering through the spaces between the 
boards, swept through the reservoir daily, from west to east, this growth dis¬ 
appeared. 

The writer is disposed to take issue with the author’s statement that soft 
water is better for all purposes. The writer has found it invariably inferior to 
hard water for rinsing soap from one’s hands after washing them, and he ventures 
to say that any one who will make a comparison in this respect between the 
soft water supplied at Atlantic City, and the relatively hard water furnished 
from the Schuylkill in Philadelphia, will agree with him. 





54 


H. D. Fisher. —Very little has been said about sterilization. I have been 
working considerably along that line, and have found, apparently, that it is 
the only way to be absolutely sure of the purity of the water. Of course, it is 
too expensive a method for a city supply, but for household use it is practicable; 
that is, the apparatus can be run at a slight cost. Our experience has been 
that it is good to boil water all the time. 

In 1898 there was a test of water-purifying apparatus at Washington, D. C., 
by a board of army officers, and this is part of the report: “Water Sterilizer: 
The foregoing apparatus has occupied considerable time on the part of the Board 
in carrying out the necessary tests of the same. As the result of numerous 
observations made with three styles of apparatus, we find that water heavily 
charged with the typhoid bacillus, the colon bacillus or the Bacillus prodigiosus, 
escapes from the apparatus entirely rid of living organisms. . . . Careful 

tests by Dr. W. M. Mew, Chemist of the Surgeon-General’s Office, show that 
there is no loss of the natural gases during the passage of the water through this 
apparatus.” 

I may add that sterilization takes that rich, beefy flavor out of Schuylkill 
water. 

“Water passing through this sterilizer, although brought to the boiling- 
point, is maintained at this temperature for so short a time as not to be deprived 
of its natural gases, and hence not rendered unacceptable to the taste. . . . 

All living micro-organisms, except a few spore-bearing bacteria, are destroyed 
by the degree of heat attained during the passage of the water through the 
apparatus. The disadvantage of the escape of a few spore-forming bacteria 
through this apparatus is considered to be of no practical importance by the 
Board. ... As the result of the exhaustive experiments, the minute 
details of which it is not considered necessary to enter into in this report, the 
Board is of the opinion that the sterilizer is superior to all filters or other water 
sterilizers submitted for trial, and that it is well adapted for the abundant supply 
of sterile water to troops serving in the field. We, therefore, after a careful 
consideration of the requirements of S. O. No. 306, A. G. O., Washington, Decem¬ 
ber 29, 1898, respectfully recommend that the Forbes Sterilizer be issued for 
the use of troops serving in the field.” 

The Board was composed of the following officers: President, Walter Reed, 
Major and Surgeon, U. S. A.; E. O. Shakespeare, Major and Surgeon, U. S. V.; 
Victor C. Vaughn, Major and Surgeon, U. S. V. 

The report was made after severe and exhaustive tests, extending over six 
months, of upward of thirty competing devices for filtering or otherwise purifying 
water. 

The cost of sterilizing water in large quantities would probably be in the 
neighborhood of $40.00 or $50.00 per million gallons, including all charges. 

In the island of Panay in the Philippines a body of soldiers were stationed 
on a mountain 6000 feet high in the interior and supplied with perfectly clear 
water from a watershed entirely free from human contamination. In spite 
of this the surgeon required all water to be sterilized, and the sickness was about 
3 per cent. This surgeon was recalled and another sent out who discontinued 
the use of the sterilizers, and inside of six weeks 75 per cent, of the men, and 
the surgeon himself, were down with intestinal troubles. Another surgeon 


55 


was sent out, and on resuming the use of the sterilizer the sickness went back 
to about 3 per cent, as before. 

J. W. Ledoux. —The author has presented to the Engineers’ Club a paper 
containing much valuable data and suggestions. He has shown us that double 
filtration, first by a rapid and coarse strainer process, and second by a fine and 
slow straining process, will produce as good results as can be obtained by the 
much more rapid and general process with the aid of a coagulant, known as 
mechanical filtration, or by the much slower process known as sand filtration. 

It is too bad that in a paper so valuable as this it is necessary to resort to 
the methods of trade publications to present the strong parts of their own devices 
and the weak parts of others. In fact, one unfamiliar with the art would 
suspect from certain portions of the paper that, with the exception of these 
designed by the author, all common types of slow sand and mechanical filter 
plants were failures. Mention is made of the large typhoid rate in Atlanta, 
Ga., and Norfolk, Va., to show that the mechanical type of filters in these places 
had failed, when, as a matter of fact, it is entirely probable that the water supply 
had absolutely nothing to do with the increase of typhoid fever during the pe¬ 
riods mentioned. 

The Chattahoochee River, which supplies Atlanta, drains an area of about 
1600 square miles of barren, sparsely inhabited, and poorly cultivated territory 
having a great deal of wooded area. There is some mining going on near the 
head-waters of the stream, but the contamination from these sources is prob¬ 
ably immaterial, and it was only necessary to filter the water because of its 
high content of turbidity, due to the washings of the red clay hills so prevalent 
in the gneissic regions of the South. 

At Norfolk, Va., the water supply is taken from Little Creek, which has a 
drainage area of about eighteen square miles, composed of flat lands largely 
wooded, and not very highly cultivated. The population is sparse, and at no 
point are there more than three or four houses close together. The storage 
reservoir is very large, containing over two thousand million gallons. It is 
entirely likely that the water supply had nothing to do with the increase of 
typhoid fever, and the principal reason for putting in the filter plant was to 
reduce the high color and remove as much as possible the vegetable matter and 
consequent swampy taste and odor. 

There is a great deal written about the relation between the water supply 
and the typhoid death-rate, but in many cases, like the two just mentioned 
it is entirely probable that they are not in any sense related. 

No doubt the author could, if he would, present data showing that the opera¬ 
tions of his filter plants had been frequently unsuccessful. Take the case of 
Lancaster, Pa. When the city was receiving propositions, the Maignen system 
of filtration was more popular than any other system of mechanical filtration 
because no coagulants were required, and no doubt a majority of the people 
believed that it would not be necessary to use coagulants, while subsequent 
conditions have proved them so essential. I would suspect from the author’s 
statement that the early results were not at all satisfactory, to overcome which 
it was necessary to introduce the principles of mechanical filtration, using sul¬ 
phate of alumina as a coagulant and soda ash to neutralize the permanent hard¬ 
ness imparted by the sulphate of alumina. This is an old device and in use 


56 


in a number of places, but usually lime is found to be cheaper and in many cases 
more satisfactory than soda. To use enough, however, to soften such water 
as the Conestoga River is an entirely different proposition, and presumably 
the author had no intention of carrying his process to that extent. 

At Charleston, S. C., where it required three grains of sulphate of alumina 
per gallon to reduce the color from 200 to 10 parts per million, it was nearly 
always necessary to use either soda ash or lime to produce sufficient alkalinity 
to decompose the sulphate of alumina, but at the Lancaster plant evidently 
the soda ash was not used for that purpose, but, as before stated, to restore 
the water to the same degree of hardness that it was before filtration. The 
Conestoga water is a limestone water, and therefore considerably harder than 
should be desirable in that section of the country. 

Regarding the process of washing in mechanical filtration; the author states 
that the filter attendant knows that the filter needs washing only by reason of 
the dirt coming through. That might be true where the sand grains are very 
large in size, or in some methods of operating the filters whereby an overdose 
of coagulant is introduced in the beginning of filtration; but our practice is 
that the need for washing the filters depends on the rise in pressure or loss of 
head. For instance, in gravity mechanical filtration the loss of head may get 
as high as 10 feet or 12 feet, while in pressure mechanical filtration the loss of 
head may go as high as 50 feet; while in each case the filters are giving their 
maximum degree of purification. 

The author shows in his filters under-drains consisting of a section similar 
to what would be produced by splitting a pipe longitudinally and made so as 
to rest on the floor, and having adjacent to this floor a series of rectangular 
slots, requiring much less fine gravel, and reducing the necessary thickness of 
the bed of filtering material; but by placing the drains closer together there is 
much less tendency to short-circuit the water-currents. In Europe, and in a 
few well designed plants in America, the under-drains consist of a row of bricks 
set on their edges and spaced several inches apart, and resting on the top of 
these another layer of bricks laid on their flats and touching each other. The 
lower course connects with the central drain. This is an excellent plan and much 
more expensive than the plan above referred to. Evidently thin concrete 
blocks can be used instead of bricks. 

In regard to sand washing for slow sand filters or those referred to by the 
author, experience has shown that the “jet” is as efficient an apparatus as can 
be devised, and the fact that this method is almost universally used in Europe 
and in the best slow sand filters of America is further evidence of its efficiency. 
There is no necessity of the fine sand being lost, and it will not if the waste water 
carrying off the dirt passes out at a low velocity. 

It has been stated during the discussion of this paper that in the design of 
a filter plant the nearer nature can be copied the more likely we are to have 
good results. By this is undoubtedly meant that if water could be obtained 
in sufficient quantity and of as good quality as contained in the wells of our 
early days, the water purification problem would be solved. It is seldom that 
shallow well-water is obtained where there is less than 50 or 100 feet of soil 
between any source of contamination and the well; so that these would at first 
sight have a great advantage over a sand filter where there is only three or 


57 


four feet of sand. To copy the well method, assuming that we have a contami¬ 
nated river, it would be only necessary to dig a large basin having sufficient 
percolating area, and then pump the river-water into the basin. Then around 
the basin, within 100 feet or so, sink wells so that they will intercept the water 
percolating from the bottom and sides of the basin. No doubt this plan would 
be very satisfactory for some time, but if the river-water is badly contaminated 
I believe the wells will eventually become contaminated also. This is proved 
by the fact that in a newly settled area wells frequently furnish a good pure 
soft water, and after the population is increased to two or three hundred the 
wells will, in the course of a few years, become foul and hard, and finally typhoid 
fever will become prevalent. This proves that it is not safe to depend on the 
continuous purifying effects of a considerable thickness of soil. Undoubtedly 
there is a thickness sufficiently great for safety, but this thickness may be meas¬ 
ured in miles instead of feet. 

Cities should adopt the purest water supply possible to get, even if it taxes 
their financial resources to the utmost, and if this water is not good enough it 
can be filtered, as it is safer to depend on a good supply filtered than a poor 
one. In looking over some of the large towns in the United States, and especi¬ 
ally Pennsylvania, it would seem that the opposite policy has been adopted. 
In several instances supplies of pure, practically uncontaminated water could 
have been obtained by gravity within a reasonable distance, but instead of 
adopting these supplies the cities have taken water from sources little better 
than open sewers, and then depend upon subsequent filtration to make the 
water fit to use. 

G. Edward Smith. —It is possible that the intestinal disorders occurring 
in filtered water districts are caused by germs that had impregnated the lining 
of the pld water pipes when they were used for raw water, and that had sub¬ 
sequently been taken up by the filtered water. Referring to the great waste 
of filtered water alluded to by Mr. Trautwine, it is probable that if meters were 
generally used the reduced consumption would result in better filtered water. 

Mr. Mebus. —There is no objection to either sterilization or household filtra¬ 
tion, if properly done. The fact is, however, that people, through lack of appre¬ 
ciation of the danger of using raw water, or through indifference or indolence, 
will not go to the trouble of boiling or filtering the drinking water. 

People of large communities expect everything supplied to them in a perfect 
state—for example, as is gas and electricity. The public health is therefore not as 
well safeguarded by dependence on individual efforts of purification as by having 
the entire public water supply purified under proper scientific supervision. 

Wm. Easby, Jr. —The paper states that the beds of a filter plant should not 
be as large as those commonly used because the resistance in the under-drains 
causes a non-uniform rate of filtration in different parts of the bed. In a well- 
designed plant this resistance is about 20 per cent, of the resistance in the clean 
sand-bed, but shortly after a bed is put in operation it becomes insignificant 
in comparison to the resistance in the surface coating. Variation in the rates 
of filtration is more largely due to non-uniformity in the grade of the sand and 
its compactness in the bed. Such a restriction in the size of beds as that sug¬ 
gested would increase the cost of construction. 


58 


P. A. Maignen. —The author has to thank the speakers of the evening for the 
very kind manner in which they have treated his paper. He agrees with Dr. 
Leffmann that the “ideal methods will be those which are able to secure the puri¬ 
fication of the water without the introduction of chemicals.” This is precisely 
what is done at South Bethlehem He also agrees with him, with the medical 
profession, and with the public authorities when they object to chemical treat¬ 
ments which make or may make the water chemically worse after treatment 
than before. 

He would strongly object to drinking-water which had been sterilized by 
any of the following compounds, which have been seriously proposed in Europe 
during the last ten years: 

Add to the water three tablets composed of the following substances: 1st 
tablet—iodid of potassium, iodid of sodium, methylene-blue; 2d tablet—tar¬ 
taric acid, sulfofuschine; 3d tablet—hyposulfite of soda (Vaillard). 

Chlorid of lime and sulfite of soda (Traube). 

Peroxid of chlorin (Berge). 

Chlorid of lime and perchlorid of iron (Duyk). 

Bromid of potassium and ammonia (Schumburg). 

The author, it will be remembered, has shown in his paper that Dr. Burlu- 
reaux and himself, as far back as 1890, established the fact that water softened 
with plain reagents such as lime and soda is at the same time sterilized without 
being injured in any way in taste or quality. 

The hard water of Canterbury and Southampton in England has been softened 
for years with lime, and no one has ever complained. The City of Columbus, 
Ohio, is going to soften all its water supply. There are in Europe thousands 
of water-softening plants, not only for industrial water but also for drinking- 
water, and these are doing most excellent work. 

The water to which alum is added on its way to house filters is rendered 
hard and unsuitable for drinking. The devices in which the alum is placed and 
from which the solution flows into the stream of raw water going to the filter 
are frequently defective. Sometimes the valves that proportionate the alum 
solution to the applied water are opened more than they ought to be, and an 
excess of the chemical is applied and goes right through the filter, passing out 
undecomposed. Such water is extremely unpleasant for bathing and wash¬ 
ing, for it does not lather, and taken with food it curdles it and renders 
digestion difficult. 

Dr. Leffmann has pointed out one of the most serious objections to the use of 
alum in the chemical treatment of water, namely, the transformation of the 
“temporary” hardness (due to bicarbonate of lime, which precipitates as mud 
in the boilers) into “permanent” hardness (due to sulphate of lime, which 
makes a “porcelain” scale). He suggests that if chemicals are to be used they 
should be introduced in the water after filtration. This would not do at Lan¬ 
caster. Here the object of the chemical treatment, as at present carried on, 
is not to modify the (chemical) quality of the water, nor to sterilize it. It is 
intended to coagulate the very fine particles of clay, which are in the water 
in immense quantities in times of flood, and to deposit them in settling tanks 
previous to filtration and thus avoid putting, at such times, any undue strain 


59 


on the filters proper. The chemical treatment has been used at Lancaster 
twenty-two days out of fifty-six in which the water was very heavily charged 
with mud. It is not likely to be resorted to more than sixty or sixty-five days 
out of three hundred and sixty-five. 

Referring to ozonization, it will be remembered that when one of the ozone 
processes was presented to the Club the author of the paper was asked what 
was the cost of the treatment, and he gave no answer. We find in the “Muni¬ 
cipal Journal and Engineer” of October 3, 1906, the following information: 
“Dr. Miquel reports that the process (Frize) has been found capable of elimi¬ 
nating a large proportion of the bacteria present in water of various descrip¬ 
tions, and of permanently destroying with certainty the bacillus coli, which 
possesses greater resisting power than the Eberth bacillus and the cholera spiril¬ 
lum. The cost of this treatment is stated, in dealing with large volumes, to 
be about centimes per cubic meter, say 1§ cents per 1000 gallons” (fifteen 
dollars per million gallons). It has been stated that water intended for ozoni¬ 
zation need not be perfectly filtered before the electric treatment is applied— 
that it is sufficient to filter it roughly. This is an error. Rough filters that 
cannot remove more than 50 per cent, of the suspended matter cannot, in times 
of flood, make the water clear enough to be acceptable to the public. Ozoni¬ 
zation, which agitates it, does not make it clear. If there be any appreciable 
quantity of suspended or dissolved organic matter in the water to which the 
process is applied, a considerable quantity of “ozone” is absorbed or neutra¬ 
lized (by this organic matter) before the process can have any effect on the 
bacteria. An imperfectly filtered water therefore is much more costly to ozonize 
than a well filtered water. All that can be stated at this time concerning ozoni¬ 
zation is that it appears to be too costly for the amount of work it does. The 
same result can be obtained by other processes which are cheaper. The elec¬ 
trical treatment therefore does not seem to have reached the stage of a practical 
proposition for application to large water supplies. 

Mr. Trautwine asks for information concerning the cost of preliminary filtra¬ 
tion. If he will turn to the author’s paper on “The Lower Roxborough Prelim¬ 
inary Filters,” published in the “Proceedings of the Engineers' Club” under 
date of April 16, 1904, he will find a full answer to the question. But for those 
who may not be able to consult these Proceedings it may be interesting to give 
here an example of the economy obtained by preliminary filtration. 

Operation .—The cost of operation of slow sand filters is estimated to vary 
from $3.00 to $5.00 per million gallons filtered. For our present purpose we 
will take $3.00 as the cost. 

The operation of preliminary filters is calculated not to exceed 75 cents 
per million gallons. 

Fixed Charges .—The installation of slow sand filters costs from $30,000 to 
$60,000 per million gallons daily capacity. For our present purpose we will 
take the lowest estimate of $30,000 and count the interest and depreciation 
at 5 per cent. 

The cost of installation of preliminary filters may be estimated at $6,000 per 
million gallons daily capacity. 


60 


When the water is treated by the plain slow sand filters alone we have: 

Operation.$3.00 per million gal. 

Fixed charges—interest and) $30,000 X 5 per m iHi on ga L 

depreciation on filters J 365 M. G. 100 

- $7.10 

When it is treated by the double process of scrubbing and 
filtering, and if we assume that 60 per cent, of the 
work is done by the scrubbers, we have: 

Operation: 

60 per cent, of the work. @ $0.75=$0.45 

40 per cent, of the work.@ $3.00=$1.20 

- $1.65 

Fixed Charges,—interest, andl S6000 X 5 ,$ 0 8 2 per million gal, 
depreciation on scrubbers J 365 M. G. 100 
The total cost of the double process therefore is: 

60 per cent, of the work.@ $0.82 = $0.49 

40 per cent, of the work.@ $4.10=$1.64 

- $2.13 $3.78 

Economy due to the use of preliminary filtration, per mil¬ 
lion gallons. $3.32 

For a plant dealing with: 

10,000,000 gallons daily, the yearly economy would be $12,118.00 
20,000,000 gallons daily, the yearly economy would be 24,236.00 
40,000,000 gallons daily, the yearly economy would be 48,472.00 
100,000,000 gallons daily, the yearly economy would be 121,180.00 

Mr. Trautwine says “our author appears willing to make the 'biological 
idea’ ridiculous by showing the absurdity of the claim which the upholders of 
that idea do not make.” Let us see whether the author has been guilty or 
foolish enough to fight a phantom. In Mr. Trautwine’s speech we find that the 
"biological idea” is represented somewhat in this wise: "The bacteria devour 
each other as we human beings devour our fellow-creatures.” "The ‘biological 
idea’ teaches us that the Schmutzdecke which forms upon the filter bed is a 
battle-field in which the bacteria mutually devour each other.” Now, this is exactly 
the idea which the author believes has not been substantiated. The bacteria 
ate the wool, they did not eat one another. In sand filters they cannot eat the 
silica. 

Micro-organisms seem to have been created for the specific purpose of decom¬ 
posing the albuminous matter of dead plants and dead animals. Cannibals 
are as rare among bacteria as among men. Place a freshly cut rose or any other 
flower, a piece of straw, or a small bundle of hay in a jar containing pure water. 
Look at a drop of this water through a microscope a fortnight afterward. You 
will see two or three kinds of animalcules of the protozoan order, which are classed 
as animals. They have some of the peculiarities of fish and some of the habits 
of rats and pigs. They live on the diminutive garbage which is in the water. 
Introduce a piece of meat in pure water; look at a drop of this water under the 
microscope in a week’s time (the infusion being kept at room temperature). 
You will find an innumerable number of exceedingly small active organisms. 















61 


Two or three weeks later these small organisms will have disappeared and their 
place will have been taken by larger and more active organisms, and you can 
judge by their apparently intelligent movements that they are engaged in the 
serious business of decomposing the organic matter into gas, water, and earth, 
with the production sometimes of toxins or other by-products. You will not 
see them eat one another. 

Take another instance—that of alcoholic fermentation in wine, cider, or 
beer. Here we have a species of organism of the yeast cell class known as 
saccharomyces ellipsoideus. The wine ferment is egg-shaped; its business 
appears to be confined to eating the sugar and transforming it into carbonic 
acid and alcohol. As long as there is any sugar in the solution the alcoholic 
ferments grow and multiply with such vim that they leave no room for any other 
kind of micro-organisms, but when all the sugar is consumed the saccharomyces 
organisms become decrepit and fall to the bottom of the vessel, constituting 
what is known as “lees” or dregs. If the wine thus fermented is clarified and 
deprived of all sediment after this first fermentation and placed in vessels free 
from water or other impurities, it will keep a number of years without any 
further decomposition. But if it is left to itself, if the air has access to it, if 
the cask in which it is stored is not strictly clean, a second kind of organism, 
the micoderma aceti, takes hold of the wine and turns it into vinegar. This 
organism is grape-shaped in form, and under favorable conditions of tempera¬ 
ture it increases so plentifully as to practically occupy all the available space. 
Sometimes, particularly when the grape juice contains leaves, stalks, and dirt, 
the secondary fermentation, instead of being acetic, is caused by putrid ferments 
of the same order as those which create putrid fermentation in water. The 
wine becomes “sick” or “ropy,” and if left to itself undergoes a series of succes¬ 
sive fermentations until it is converted into water and earth. The organism 
which causes the sickness in wine is of a filamentous appearance, a bacillus. 
While this putrid fermentation is going on, you see one kind of organism pre¬ 
vailing at one time and another kind at another time. As far as the author 
knows, they do not eat one another, they live the natural span of their allotted 
life, and when the appropriate food is all consumed they die, giving place some¬ 
times to other kinds with different tastes, and these also in the end die out 
unless they are transferred into pastures new. 

How Long Do Typhoid, Germs Live In Water ?—You will remember the table 
presented by the author showing that typhoid bacilli die in distilled water in a 
short time. Is it because they do not find appropriate food in the distilled 
water? Or it may be that the distilled water itself is impure and contains 
dissolved metallic salts absorbed from the glass or metallic vessels in which it is 
distilled or stored. The question remains open. 

We have often been told that typhoid bacilli are destroyed by the ordinary 
water bacteria, and now Mr. S. J. Lewis, in the paper already alluded to, tells 
us that the bacillus of typhoid fever conquers the water bacteria. The full 
text of Mr. Lewis’ paper is as follows—(U. S. Geological Survey, Paper No. 
161, page 75): 

“The anthrax bacillus and its spores, the staphylococcus pyogenes aureus 
(the organism of pus) and the typhoid bacillus can retain their life a very long 
time in water. Karondi found that the ordinary water bacteria multiplied 


62 


greatly for a time after the introduction of the pathogenic organisms and then 
began to die out, and that for varying periods the foul water, being kept at 
room temperature, was found to contain pure culture of the disease-producing 
organisms which retained full virulence up to complete evaporation. For the 
anthrax bacillus and its spores the period of life varied from 264 to 816 days, 
the water bacteria in the medium having completely disappeared after three 
or four weeks. The pus organism was found in pure culture after two months 
and retained its virulence for 508 days. The bacillus of typhoid fever showed 
similar power of conquering the water bacteria which lived in the medium for 
four months, at the end of which time the bacillus typhosus was in pure cul¬ 
ture, living in ordinary tap w’ater at room temperature for 499 days. What 
more evidence is needed of the ability of the organisms of water-borne disease 
to poison a water as far as drinking purposes are concerned for a long time, 
admitting the pollution to cease instead of continuing as in the cases under 
consideration?” 

The authQr thinks that the word “ outliving” would be more appropriate 
than the word “conquering” used above. 

Typhoid Not Always Due to Pre-existing Cases .—There is just now a great 
controversy about typhoid fever. We are told that during the present year 
there has been a great wave of typhoid throughout the country. Certain 
cities which have modern filter plants have been seriously afflicted and atten¬ 
tion has been drawn to what is called “residual causes,” such as milk, fruit, 
vegetables, and wells. But while we acknowledge that these “residual” causes 
may account for stray cases, epidemics are always due to water pollution. It 
is thought that this pollution must necessarily come from sewage containing 
the specific germs issued from typhoid patients. While we are not prepared 
to deny this theory, we ought not to shut our eyes to the fact that sporadic cases 
may also occur without pre-existing cases; thus, the infection may come from 
the decomposition of animals drowned in wells, or from vegetable or animal 
matter decaying in pools, ditches, and swamps. The bacteria bred in these 
stagnant waters may easily find their way in flood times into the water-courses. 
Typhoid and all intestinal disorders are practically filth diseases. Water sup¬ 
plies which are sometimes said to be above suspicion may all of a sudden become 
infected by filth, as at Plymouth, Pa., and as is probably the case now at Scran¬ 
ton, Pa. It may, therefore, be laid down as an obligation on the part of munici¬ 
palities to see to it that all the water supplies be carefully purified, and it behooves 
every householder to make sure that the water used by the family is purified 
at home. Although the water of London is filtered by the municipality, there 
is hardly a house in the great metropolis without some sort of domestic filter. 

The estimate of Messrs. Hering, Gray and Wilson comparing the cost of 
mechanical and of slow sand filtration and showing that there is very little 
difference between the estimated total cost of the two systems—fixed charges 
and maintenance—is true of most other estimates, but as a general proposition 
if the depreciation is taken into serious consideration the mechanical system 
is likely to be the more costly in the long run. 

Referring to the so-called “English” or plain slow sand filters, we often hear 
it said that they are good enough to be copied without being improved upon. 
It should be stated in a discussion of this kind that they have not always been 


63 


perfect. Thus, Mr. Ripley Nichols, in his book entitled “Water Supply" 
(page 159), gives the following table showing the efficiency of the London slow 
sand filters: 


TABLE XXII.—THAMES AND LEA WATER.—COMPARATIVE EFFI¬ 
CIENCY OF DIFFERENT RATES OF FILTRATION DURING 
THE YEARS 1868 TO 1873, INCLUSIVE. 


Name of Company. 

Maximum Rate 
of Filtration 

Number of Monthly Occasions When: 

Expressed in 
Inches per 
Hour. 

Clear. 

Slightly 

turbid. 

Turbid. 

Very 

Turbid. 

Thames: 






Chelsea. 

7.27 

49 

15 

5 

6 

West Middlesex. 

4.71 

75 

0 

0 

0 

Southwark and Vauxhall .. 

6.00 

41 

24 

5 

4 

Grand Junction. 

6.97 

55 

14 

7 

0 

Lambeth. 

12.00 

42 

11 

12 

10 

Lea: 





New River. 

5.00 

70 

4 

0 

0 

East London. 

3.85 

51 

18 

3 

2 


It will be observed in this table that the West Middlesex Company has had 
clear water all the time. This is due to two factors: The water of the Company 
was taken at a higher point up the Thames River than that of the other com¬ 
panies, and in addition it was (if the author remembers correctly) made to pass 
into gravelly soil—after the fashion of filter galleries—before reaching the 
filters proper. The New River Company made a better showing than the East 
London Company, because it also takes its supply much closer to the source 
of the River Lea. As a general rule, the water intended to go through the 
London filters is stored in large sedimentation reservoirs, which have some¬ 
times been called “stagnant pools," and in which, in the summer, weeds and 
algae grow to a very great extent under the influence of the sunlight. These 
algae die after a cloudy or rainy day and give a bad taste to the water. In the 
spawning season the fish spawn comes to the filters in such quantity as to clog 
them sometimes in a few hours. The London companies, as the author under¬ 
stands, are now trying preliminary filtration to help their plain slow sand filters. 

In a report on “Filter Tests," made by Dr. Med. Karl Schreiber, of Berlin, 
we read the following observations concerning the sand washing operation: 
“Rapid filtration possesses a great advantage as compared with slow sand 
filtration in the method of washing. For this purpose in slow sand filtration 
workmen must enter the filter. The sand is generally transported outside 
in wheelbarrows, and during this, as well as during washing and during the 
transportation back to the filter, it comes into contact with the hands and the 
dress of the workmen. In winter this process of cleaning may not be required 
for months, while in summer it may become necessary very frequently, in con¬ 
sequence of which a sudden increase of the working force may be required, 
and it may then not always be possible to examine the men in regard to their 
health, which circumstance certainly involves the danger of an infection, es- 
























64 


pecially during an epidemic. In a rapid filter plant, however, washing is done 
entirely mechanically; the workmen do not come into any contact whatever 
with the filter bed or with the water.” The author must confess that “the 
contact of the sand with the hands and dress of the workmen” does not appear 
to be so great a danger as is suggested by the Berlin critic. 

We find in the same report the following statement: “In case a rapid filter 
plant should happen to become infected by pathogenic germs, then a disinfec¬ 
tion of the entire plant by sterilization can readily be made at a small cost. 
In slow sand filtration the filters cover so large a space that this in itself would 
make disinfection very difficult.” 

Are we to understand that the mechanical or the slow sand filters intended 
to furnish cities with pure drinking-water can, at any time, become infected— 
that the germs of disease which they retain at one time can be given back to 
the water at another? What a disillusion this must be for those who think 
that these large municipal filters are absolutely safe methods of protection against 
water-borne diseases! The fact is that the danger in question does exist. We 
can conceive of large plain slow sand filters being so constructed and operated 
as to be liable to infection, but we also know that they can be designed so as 
to remain perfectly safe at all times, and one of the best means to bring about 
this safe condition is to prepare the water as thoroughly as possible by such 
method as preliminary filtration before admission to the final slow sand filters. 
The management of mechanical filters may be of such superior kind as to give 
safe water all the time, but the author must confess that this is a very difficult 
thing. If the chemical reaction or sterilization is not complete the filtration 
cannot make the water safe. One of the best ways to improve the work of the 
mechanical filters would be to subject the water to preliminary filtration pre¬ 
vious to final rapid filtration so as to avoid the necessity of frequent cleaning, 
which, as has been explained, is the bane of the system, not only in matter 
of cost but also in matter of efficiency. 

Another record in favor of double filtration comes from Kittanning, Pa., 
where a double semi-rapid filter plant was erected upon the design of the author 
and placed in service on'}February 19, 1905. The following is the report of 
the local Board of Health: 


1904 .103 cases 8 deaths 

1905 . 25 “ 2 “ 

1906 . 8 “ 0 “ 


Mr. Trautwine finds fault with the soft water of Atlantic City, and with soft 
water in general because he says he cannot wash the soap off his hands. Accus¬ 
tomed as he is to make a liberal use of soap with hard water, it is evident that 
he uses too much soap with the soft water. He should use less soap and he 
would require less water to rinse it off. The English ladies are very fond of 
soft water because it enables them to use very little soap. 

Mr. Trautwine asks why the reagents used first at Lancaster (with a view 
of softening the water) were abandoned and other reagents substituted. The 
author replies: because the people of Lancaster were not ripe for the improve¬ 
ment. To tell the people of that city, and particularly the fault-finders, that 
it would be better for them if the Conestoga water were softened, would be like 





65 


telling Mr. Trautwine that soft water is better for rinsing soap off the hands 
than hard water. Any change in the chemical composition of the water was 
looked upon by the authorities as courting discussion. The yellow journals 
were continually on the lookout for anything that might discredit the admin¬ 
istration which had presided over the installation of the filter plant. One day 
a local druggist rushed to the Mayor’s office with a bottle of water in which 
he said he had detected alum. Mysterious whisperings went through the ranks 
of the opposition leaders; the filter plant had been detected at fault. What joy! 

Upon investigation it was found: 

1. That no chemicals of any description had been used at the filter plant for 
more than three weeks previous to the collection of the suspected sample. 

2. The local druggist had added ammonia to the water as a reagent and 
had obtained thereby a flocculent precipitate which he at once labeled alum. 

3. The sample was submitted to Dr. Samuel P. Sadtler and son, of Phila¬ 
delphia, who pronounced the precipitate to be due, not to alum, but to magnesia 
—one of the natural constituents of the Conestoga water. 

When the question of chemical purification of the water was being considered 
by the administration of Lancaster it was thought undesirable to change its 
chemical quality in any way. It was suggested that the people were accus¬ 
tomed to the Conestoga water “nature” with its lime and magnesia, and that 
any change, even for the better, would be found fault with. This is why the 
water-softening process was' not persevered in and the treatment was limited 
to a purely physical coagulation. The author has no doubt that before very 
long the advantages of soft water will dawn on the good people of Lancaster 
and that the softening treatment will be ultimately called for. 

In this connection we find in the U. S. Geological Survey, Paper No. 161, 
sentences like the. folio wing: “The quality of the water is fairly good for drinking 
purposes, though too high in mineral matters for commercial use.” “These 
waters are all hard rock water suitable for drinking purposes but high in incrus- 
tating and corroding solids and therefore unfit for use in boilers.” The able 
geologist is somewhat at fault in things physiological. Hard water is never 
good for drinking. If it is capable of making incrustations in boilers it also 
makes incrustations in animal articulations. This has been clearly established 
in Europe for years. “Waters which contain lime or other mineral salts which 
are not naturally in the organism,” says the Sixth International Pharmaceu¬ 
tical Congress, Brussels, 1888, “form, with the chyle, an abnormal medium for 
hematosis (formation of blood). They fatigue the kidneys and incrust the 
articulations.” 

Artificial Filtering Membrane. —Mr. Trautwine “has been informed by experts 
that the asbestos film (deposited on the sand) was open to the objection that 
air-bubbles formed under it,” and he takes it for granted “that the particles 
of charcoal and of coke fail to unite in a continuous film, easy of removal, as 
the asbestos particles did.” In his experiments with asbestos the author has 
not been much disturbed by air. This phenomenon of air-bubbles occurs mostly 
within a few days or a few weeks of placing the filter in service for the first 
time. Afterward it does not occur. Although the charcoal or coke powder can¬ 
not be rolled like an asbestos blanket, it is as easily removed from the sand as 
5 


66 

ordinary mud, and therefore it does not offer any difficulty in operation or in 
cost. 

Natural Filtration .—Under the generic title “ natural filtration” Mr. Lewis 
includes “filter wells,” “filter galleries,” and “filter cribs.” He describes 
the filter wells in use at Monongahela, Braddock, and other West Virginia towns; 
the filter galleries established at Woburn, Mass., Lowell, Mass., Indianapolis, 
Ind., Columbus and Springfield, Ohio; the filter cribs of Montrose, Pa., Tarentum, 
Pa., Hulton, Pa., Sharpsburg, Pa., Etna, Pa., Milvale, Pa., and Wildwood, Pa., 
etc. 

The “filter wells” are generally about 20X20 feet. They are sunk at a 
little distance from the river (30 feet at Braddock). The water of the running 
stream is supposed to seep through the sand and gravel of its own bed and 
pass into the well. In no case have the results been satisfactory. At Braddock, 
for instance, there were in 1900 one hundred cases of typhoid fever in a popula¬ 
tion of 16,654. 

Filter galleries are open drains laid in gravelly soil into which river-water 
or ground-water penetrates and from which it is drawn or pumped, and the 
water so filtered is supposed to be purified. Mr. Lewis says: “The filtration 
in filter galleries only clears the water of visible impurities, frequently making 
it doubly dangerous by masking the pollution. The device, when successful, 
is merely a form of well that has much greater collecting surface than the ordi¬ 
nary well can have, collecting ground-water in the same way as an ordinary 
shallow well and subject to the same contamination from accidental pollution.” 
All the filter galleries described by Mr. Lewis have practically failed to give 
good water. 

Filter cribs have had no better success. The bacterial analyses of the water 
drawn from the cribs show, if anything, an increase in the number of germs 
as compared with the river-water which it was intended to purify. The crib 
of Montrose is 2,500 feet long, 32 feet wide, 7 feet deep, its framework having 
been built of 6-inch X 8-inch hemlock timbers laid flat. The timbers are spread 
by blocks 4 inches thick, spaced about 3 feet apart. It is tightly planked over 
on top with 3-inch planks, but its sides and bottom are open. In placing the 
crib an excavation somewhat larger than the area of the structure was made 
and the crib was floated over and sunk into place. It is covered with stones 
and coarse gravel with sand on top. The average depth of gravel and sand 
on the crib is 5 feet. The depth of the crib below surface at low water is 16 
feet at the upper end and 10 feet at the lower. 

In all these so-called systems of natural filtration—wells, galleries, cribs— 
the filtration goes on finely for some hours, days, weeks, or months, but if the 
applied water be at all roily the sand and gravel soon become saturated or clogged 
with mud, then either' the water ceases to come through, or, if it does come 
through, it is not filtered. It passes in fissures, “rat holes,” or open chan¬ 
nels, which have no more effect in purifying water than plain cast-iron pipes. 
It is easy enough to separate mud from water by filtration, but it is not a 
simple matter to remove the mud from the materials which have collected it. 
It is difficult enough with slow sand filters and with mechanical filters, but 
it is altogether impossible with filter wells, filter galleries, or filter cribs. Such 
devices, therefore, are nothing but a delusion and a snare. 


67 


Mr. Fisher has described an apparatus called water sterilizer. The principa 
advantage claimed for this apparatus over the ordinary methods of boiling 
water is that it “can be run at a small cost” for fuel, owing to the exchange of 
heat units between the incoming cold water and the outgoing hot water, and 
that the water cannot get out of the apparatus unless it has been raised to the 
boiling-point. According to the report quoted by Mr. Fisher, “the living or¬ 
ganisms are destroyed” by boiling, but “the spore-bearing bacteria are not 
destroyed by the degree of heat (212° F.) attained during the passage of the 
water through the apparatus.” The French and German sterilizers based upon 
the same exchange system keep the water during a few minutes at a temperature 
of 120° C. (248° F.), and this is supposed to kill the spore-bearing bacteria. 
Prof. Tyndal years ago demonstrated that to sterilize water it was necessary 
to boil it three times on three subsequent occasions, allowing several days to 
elapse between each boiling. The spores or dry germs are heated and wetted 
during the process and presumably incubated, developing finally into adult 
or living bacteria. In this advanced stage of existence they are easily killed 
by boiling. A report presented to the French Acad6mie des Sciences on February 
19, 1906, by Messrs. Calmette and Breton shows that animals (guinea-pigs) 
were seriously affected by being made to drink or by being inoculated with 
water which had been polluted with tubercle bacilli and boiled. The animals 
previously weak were killed, and others* until then healthy, were made sick, 
with all the symptoms of tuberculosis. This finding has caused some French 
technical papers to say, “What is the use of boiling the water if the bacilli 
are not less dangerous dead than alive?” No explanation of this persistence 
of the danger in boiled water has been given. We may, therefore, suppose three 
things: (1) it may be that the simple boiling does not destroy all the bacilli, 
or (2) that it does not decompose or neutralize the dissolved “toxins,” (3) or 
that the harm may be done by what is known as “fixed” toxins which remain 
in or on the body of the bacilli after boiling. 

Mr. Ledoux says: “It is too bad . . . that the author . . . had 

to resort to the methods of trade publications to present the strong parts of 
their own devices and the weak parts of others.” 

Is it a crime to be prejudiced in favor of one’s own inventions? The author 
does not hesitate to say that he is strongly in favor of slow sand filtration, which 
he has studied particularly during the last ten years. Will Mr. Ledoux deny 
that he also is prejudiced in favor of mechanical filtration, which he has improved 
and used in numerous waterworks for which he is engineer? 

The author is not conscious of having been unfair to any person or system. 
He has not stated that “all common types of slow sand and mechanical filter 
plants were failures.” He said that some (not all) of the slow sand filters and 
some (not all) of the mechanical filters had at certain times failed to give the 
results expected. 

The author is not the only one nor the first to r point out that “common types 
of slow sand and mechanical filter plants” were not always a success. Thus, 
for instance, Mr. Geo. W. Fuller, in “Transactions of the American Society 
of Civil Engineers,” vol. 1, 1903, page 471, says: “While, as is well known, 
in the majority of cases, mechanical filters have not been operated in a manner 
to produce uniformly good results, it is a fact, which does not seem to be appre- 


68 


dated by many, that the majority of the larger sand filters in this country that 
have been operated for several years have also failed to reach the goal which 
may be expected of them, as is noted by any one who takes the trouble to examine 
carefully the typhoid fever experiences in cities which have sand filters, such 
as Poughkeepsie, Hudson, and Little Falls, N. Y., Ashland, Wis., Rock Island, 
Ill., etc.” 

The author endeavored in his original paper to avoid saying anything unkind 
of mechanical filters; he simply wdshed to draw attention to the fact that the 
water filtered during the first half hour after washing ought to be wasted, and 
even this he mentioned only because some engineers have suggested that it 
would not materially lower the average effluent if mixed with the filtrate of 
other filters and that therefore it should not be wasted. 

Mr. Ledoux having entered on the w r ar-path in favor of mechanical filtration, 
the author is bound to refer to various statements which may help to establish 
the truth. The allusion to Atlanta and Norfolk is to be found in the “ Engineer¬ 
ing News,” November 8, 1906, in the paper of Mr. Theodore Horton, who says: 
“The cases of typhoid fever during July, August, and September, 1906, were 
more than during the corresponding months for 1904 and 1905.” 

Referring to mechanical filters, Mr. Geo. W. Fuller, already quoted, is reported 
to have said (Senate Paper on the “Purification of the Washington Water 
Supply,” page 203): “If the merits of filters of this type were to be judged 
from the general knowledge as to their efficiency as now’ obtained in practice 
in the majority of cases, the indications are that it would not receive a rating 
of the highest grade. This seems to be due in part to a lack of the necessary 
skilled supervision at small plants and in part to a desire to avoid the expense 
of applying a sufficient quantity of coagulant.” In the same report, page 101, 
Lieut.-Col. Charles Smart says: “The rapidity of the filtration and the fre¬ 
quent disturbance of the sand precluded the idea of a satisfactory removal 
of bacteria.” Again, in the same report, page 133, we find: 

TABLE IY.—SHOWING THE AVERAGE NUMBER OF DEATHS FROM 
TYPHOID FEVER PER ANNUM AFTER FILTRATION 
TO 10,000 POPULATION. 

Mechanical Filters. 


Name op Town. 

Average Num¬ 
ber of Deaths 
from Typhoid 
Fever per An¬ 
num before 
Filtration: 

Average Num¬ 
ber of Deaths 
from Typhoid 
Fever after 
Filtration. 

Per Cent. 
Increase. 

Number of 
Years upon 
which Sta¬ 
tistics ARE 
BASED BEFORE 
AND AFTER 

Filtration. 

Newcastle, Pa. 

1.3 

2.8 

115 

1 

Lexington, Ky. 

1.8 

6.4 

256 

4 




Mr. Ledoux says: “It is entirely probable that the water supply has absolutely 
nothing to do with the increase of typhoid fever during the periods mentioned.” 
This is a supposition which any one can make, but the evidence afforded by 
Scranton, Ithaca, Butler, and Plymouth, seems to prove that water is the prin¬ 
cipal vehicle of typhoid fever, and it is a little late in the day to attempt to throw 

















69 


the blame of typhoid on anything but the water supply. The so-called u resid¬ 
ual causes of typhoid, such as milk, vegetables, fruit, and well-water, may 
account for some cases, but these causes have always existed and will always 
exist. If anything, they have been improved of late. It seems, therefore, 
perfectly fair to judge of the success of a filtration system by its effect upon the 
morbidity and mortality of the inhabitants. 

Mr. Ledoux suggests “that the application of the principles of mechanical 
filtration to the Lancaster filter plant was an after-thought resulting from a 
failure.” Our critic is mistaken; it was part of the original design, as explained 
in the paper, to meet the exceptional need of the water in time of flood, and 
at no other time. 

Mr. Ledoux cites his experience concerning the indication for cleaning mechani¬ 
cal filters, and he says that he knows of no other than the rising pressure or the 
loss of head, which may vary from 10 feet to 50 feet, and he does not agree 
with the author, whom he quotes as saying that “the filter attendant knows 
that the filter needs washing (only) by reason of the dirt coming through.” 
The author did not say “only,” and his information was gathered in part from 
the following references: 

Report of Mr. Geo. W. Fuller on the investigations of Louisville, 1898, page 
97: “Decision to Wash the Filter .—This decision was one which required consider¬ 
able judgment. During the whole test no case was recorded where the Warren 
filter was washed on account of the entire available head having been used, 
and the rate falling below the desired quantity. In fact, less than 60 per cent, 
of the available head obtained with the weir (4.17 feet) was ordinarily utilized. 
In general, it may be stated that the only immediate guide to the decision to 
wash the filter at any particular time was the appearance of the effluent.” Page 
101: “Unsatisfactory appearance of the effluent and a utilization of the total 
available' head were the immediate guides to washing.” (Jewell filter.) Page 
103: “Either the unsatisfactory appearance of the effluent or the decrease 
in the rate of filtration on account of resistance of the filter were used as imme¬ 
diate guides for the determination of the time of washing.” (Western gravity 
filter.) The author also refers to the report of the Sewerage and Water Board, 
New Orleans, 1903, page 137: “Decision to Wash the Filters .—It was necessary, 

as a rule, to operate the filter until the loss of head reached the available limit— 
10.7 feet—provided the appearance of the effluent was satisfactory.” (This 
refers to filters Nos. 3 and 4 of the Experimental Station.) 






























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